Hazardous material canister systems and methods

ABSTRACT

Techniques for inspecting a weld of a nuclear waste canister include positioning a gamma ray image detector near a nuclear waste canister that encloses nuclear waste. The nuclear waste canister includes a housing that includes a volume in which the waste is enclosed and a top connected to the housing with at least one weld to seal the nuclear waste in the nuclear waste canister. The techniques further include receiving, at the gamma ray image detector, gamma rays from the nuclear waste that travel through one or more voids in the weld; generating an image of the received gamma rays with the gamma ray image detector; and based on the generated image, determining an integrity of the at least one weld.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119 to: U.S.Provisional Patent Application Ser. No. 62/808,594, filed on Feb. 21,2019; U.S. Provisional Patent Application Ser. No. 62/808,516, filed onFeb. 21, 2019; U.S. Provisional Patent Application Ser. No. 62/808,591,filed on Feb. 21, 2019; U.S. Provisional Patent Application Ser. No.62/808,570, filed on Feb. 21, 2019; U.S. Provisional Patent ApplicationSer. No. 62/808,571, filed on Feb. 21, 2019; and U.S. Provisional PatentApplication Ser. No. 62/808,745, filed on Feb. 21, 2019. The entirecontents of each of the previous applications are incorporated byreference herein.

TECHNICAL FIELD

This disclosure relates to hazardous material canister systems andmethods.

BACKGROUND

Hazardous material, such as radioactive waste, is often placed inlong-term, permanent, or semi-permanent storage so as to prevent healthissues among a population living near the stored waste. Such hazardouswaste storage is often challenging, for example, in terms of storagelocation identification and surety of containment. For instance, thesafe storage of nuclear waste (e.g., spent nuclear fuel, whether fromcommercial power reactors, test reactors, or even high-grade militarywaste) is considered to be one of the outstanding challenges of energytechnology. Safe storage of the long-lived radioactive waste is a majorimpediment to the adoption of nuclear power in the United States andaround the world. Conventional waste storage methods have emphasized theuse of tunnels, and is exemplified by the design of the Yucca Mountainstorage facility. Other techniques include boreholes, including verticalboreholes, drilled into crystalline basement rock. Other conventionaltechniques include forming a tunnel with boreholes emanating from thewalls of the tunnel in shallow formations to allow human access.

SUMMARY

In a general implementation, a method for inspecting a weld of a nuclearwaste canister includes positioning a gamma ray image detector near anuclear waste canister that encloses nuclear waste. The nuclear wastecanister includes a housing that includes a volume in which the waste isenclosed and a top connected to the housing with at least one weld toseal the nuclear waste in the nuclear waste canister. The method furtherincludes receiving, at the gamma ray image detector, gamma rays from thenuclear waste that travel through one or more voids in the weld;generating an image of the received gamma rays with the gamma ray imagedetector; and based on the generated image, determining an integrity ofthe at least one weld.

In an aspect combinable with the general implementation, the nuclearwaste includes spent nuclear fuel.

In another aspect combinable with any of the previous aspects, the spentnuclear fuel includes at least one spent nuclear fuel assembly.

In another aspect combinable with any of the previous aspects, the gammaray image detector includes a pinhole camera or an Anger camera.

In another aspect combinable with any of the previous aspects, at leastone of the housing, the top, or a weld material includes a corrosionresistant alloy.

In another aspect combinable with any of the previous aspects, each ofthe housing, the top, and the weld material includes the corrosionresistant alloy.

In another aspect combinable with any of the previous aspects, thecorrosion resistant alloy includes CRA 625.

In another aspect combinable with any of the previous aspects, the atleast one weld includes a horizontal weld.

In another aspect combinable with any of the previous aspects, receivingthe gamma rays includes receiving a plurality of gamma rays that emitfrom the nuclear waste and scatter through the volume of the nuclearwaste container and through one or more voids in the one or more weldstoward the gamma ray image detector.

Another aspect combinable with any of the previous aspects furtherincludes rotating at least one of the nuclear waste canister or thegamma ray image detector during the receiving, at the gamma ray imagedetector, of the gamma rays from the nuclear waste that travel throughthe one or more voids in the weld.

In another aspect combinable with any of the previous aspects, therotating includes rotating at least one of the nuclear waste canister orthe gamma ray image detector for 360 degrees.

In another aspect combinable with any of the previous aspects, the atleast one weld that connects the top to the housing includes a sealformed with a direct material deposition system.

In another general implementation, a system for inspecting a weld of anuclear waste canister includes a nuclear waste canister that enclosesnuclear waste, and a gamma ray image detector system positioned adjacentthe nuclear waste canister. The nuclear waste canister includes ahousing that includes a volume configured to enclose the nuclear wasteand a top connected to the housing with at least one weld to seal thenuclear waste in the nuclear waste canister. The gamma ray imagedetector system is configured to perform operations including receivinggamma rays from the nuclear waste that travel through one or more voidsin the weld; generating an image of the received gamma rays with atleast one gamma ray image detector; and based on the generated image,determining an integrity of the at least one weld.

In an aspect combinable with the general implementation, the nuclearwaste includes spent nuclear fuel.

In another aspect combinable with any of the previous aspects, the spentnuclear fuel includes at least one spent nuclear fuel assembly.

In another aspect combinable with any of the previous aspects, the gammaray image detector system includes a pinhole camera or an Anger camera.

In another aspect combinable with any of the previous aspects, at leastone of the housing, the top, or a weld material includes a corrosionresistant alloy.

In another aspect combinable with any of the previous aspects, each ofthe housing, the top, and the weld material includes the corrosionresistant alloy.

In another aspect combinable with any of the previous aspects, thecorrosion resistant alloy includes CRA 625.

In another aspect combinable with any of the previous aspects, he atleast one weld includes a horizontal weld.

In another aspect combinable with any of the previous aspects, the gammaray image detector system is configured to receive a plurality of gammarays that emit from the nuclear waste and scatter through the volume ofthe nuclear waste container and through one or more voids in the one ormore welds.

In another aspect combinable with any of the previous aspects, at leastone of the nuclear waste canister or the gamma ray image detector systemis configured to rotate during operation of the gamma ray image detectorsystem to receive the gamma rays from the nuclear waste that travelthrough the one or more voids in the weld.

In another aspect combinable with any of the previous aspects, the atleast one of the nuclear waste canister or the gamma ray image detectorsystem is configured to rotate 360 degrees during operation of the gammaray image detector system to receive the gamma rays from the nuclearwaste that travel through the one or more voids in the weld.

In another aspect combinable with any of the previous aspects, the atleast one weld that connects the top to the housing includes a sealformed with a direct material deposition system.

Implementations of a hazardous material storage repository according tothe present disclosure may include one or more of the followingfeatures. For example, a hazardous material storage repository accordingto the present disclosure may allow for multiple levels of containmentof hazardous material within a storage repository located thousands offeet underground, decoupled from any nearby mobile water. As anotherexample, implementations of a hazardous material canister according tothe present disclosure may be more easily deployed in a hazardousmaterial storage repository, while also being less susceptible tobreakage or leakage of hazardous material stored therein due to aseismic event, such as an earthquake. As another example,implementations of a hazardous material canister according to thepresent disclosure may be more easily and efficiently inspected, e.g.,to ensure that there are no leakage paths from an inner volume of thecanister to an ambient environment. For instance, implementations of ahazardous material canister that include one or more welds may be moreeasily and efficiently inspected to ensure that there are little to novoids in the one or more welds using gamma ray radiography that includesa radioactive source internal to the hazardous material canister. As yetanother example, implementations of a hazardous material canisteraccording to the present disclosure may be more easily and efficientlysealed through, e.g., a spin welding or direct material depositionprocess.

The details of one or more implementations of the subject matterdescribed in this disclosure are set forth in the accompanying drawingsand the description below. Other features, aspects, and advantages ofthe subject matter will become apparent from the description, thedrawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an example implementation of ahazardous material storage repository that includes one or morehazardous material canisters according to the present disclosure.

FIG. 2 is a schematic illustration of another example implementation ofa hazardous material storage repository that includes one or morehazardous material canisters according to the present disclosure.

FIGS. 3A-3D are schematic illustrations of example implementations of aspherical hazardous material canister according to the presentdisclosure.

FIG. 4-8 are schematic illustrations of example implementations of ahazardous material canister according to the present disclosure.

FIG. 9 is a schematic illustration of a controller or control systemaccording to the present disclosure.

DETAILED DESCRIPTION

FIG. 1 is a schematic illustration of an example implementation of ahazardous material storage repository system 100, e.g., a subterraneanlocation for the long-term (e.g., tens, hundreds, or thousands of yearsor more), but retrievable, safe and secure storage of hazardous material(e.g., radioactive material, such as nuclear waste which can be spentnuclear fuel (SNF) or high level waste, as two examples). For example,this figure illustrates the example hazardous material storagerepository system 100 once one or more canisters 126 of hazardousmaterial have been deployed in a subterranean formation 118. Asillustrated, the hazardous material storage repository system 100includes a drillhole 104 formed (e.g., drilled or otherwise) from aterranean surface 102 and through multiple subterranean layers 112, 114,116, and 118. Although the terranean surface 102 is illustrated as aland surface, terranean surface 102 may be a sub-sea or other underwatersurface, such as a lake or an ocean floor or other surface under a bodyof water. Thus, the present disclosure contemplates that the drillhole104 may be formed under a body of water from a drilling location on orproximate the body of water.

The illustrated drillhole 104 is a directional drillhole in this exampleof hazardous material storage repository system 100. For instance, thedrillhole 104 includes a substantially vertical portion 106 coupled to aradiussed or curved portion 108, which in turn is coupled to asubstantially horizontal portion 110. As used in the present disclosure,“substantially” in the context of a drillhole orientation, refers todrillholes that may not be exactly vertical (e.g., exactly perpendicularto the terranean surface 102) or exactly horizontal (e.g., exactlyparallel to the terranean surface 102), or exactly inclined at aparticular incline angle relative to the terranean surface 102. In otherwords, vertical drillholes often undulate offset from a true verticaldirection, that they might be drilled at an angle that deviates fromtrue vertical, and inclined drillholes often undulate offset from a trueincline angle. Further, in some aspects, an inclined drillhole may nothave or exhibit an exactly uniform incline (e.g., in degrees) over alength of the drillhole. Instead, the incline of the drillhole may varyover its length (e.g., by 1-5 degrees). As illustrated in this example,the three portions of the drillhole 104—the vertical portion 106, theradiussed portion 108, and the horizontal portion 110—form a continuousdrillhole 104 that extends into the Earth. As used in the presentdisclosure, the drillhole 104 (and drillhole portions described) mayalso be called wellbores. Thus, as used in the present disclosure,drillhole and wellbore are largely synonymous and refer to bores formedthrough one or more subterranean formations that are not suitable forhuman-occupancy (i.e., are too small in diameter for a human to fittherewithin).

The illustrated drillhole 104, in this example, has a surface casing 120positioned and set around the drillhole 104 from the terranean surface102 into a particular depth in the Earth. For example, the surfacecasing 120 may be a relatively large-diameter tubular member (or stringof members) set (e.g., cemented) around the drillhole 104 in a shallowformation. As used herein, “tubular” may refer to a member that has acircular cross-section, elliptical cross-section, or other shapedcross-section. For example, in this implementation of the hazardousmaterial storage repository system 100, the surface casing 120 extendsfrom the terranean surface through a surface layer 112. The surfacelayer 112, in this example, is a geologic layer comprised of one or morelayered rock formations. In some aspects, the surface layer 112 in thisexample may or may not include freshwater aquifers, salt water or brinesources, or other sources of mobile water (e.g., water that movesthrough a geologic formation). In some aspects, the surface casing 120may isolate the drillhole 104 from such mobile water, and may alsoprovide a hanging location for other casing strings to be installed inthe drillhole 104. Further, although not shown, a conductor casing maybe set above the surface casing 120 (e.g., between the surface casing120 and the surface 102 and within the surface layer 112) to preventdrilling fluids from escaping into the surface layer 112.

As illustrated, a production casing 122 is positioned and set within thedrillhole 104 downhole of the surface casing 120. Although termed a“production” casing, in this example, the casing 122 may or may not havebeen subject to hydrocarbon production operations. Thus, the casing 122refers to and includes any form of tubular member that is set (e.g.,cemented) in the drillhole 104 downhole of the surface casing 120. Insome examples of the hazardous material storage repository system 100,the production casing 122 may begin at an end of the radiussed portion108 and extend throughout the horizontal portion 110. The casing 122could also extend into the radiussed portion 108 and into the verticalportion 106.

As shown, cement 130 is positioned (e.g., pumped) around the casings 120and 122 in an annulus between the casings 120 and 122 and the drillhole104. The cement 130, for example, may secure the casings 120 and 122(and any other casings or liners of the drillhole 104) through thesubterranean layers under the terranean surface 102. In some aspects,the cement 130 may be installed along the entire length of the casings(e.g., casings 120 and 122 and any other casings), or the cement 130could be used along certain portions of the casings if adequate for aparticular drillhole 104. The cement 130 can also provide an additionallayer of confinement for the hazardous material in canisters 126.

The drillhole 104 and associated casings 120 and 122 may be formed withvarious example dimensions and at various example depths (e.g., truevertical depth, or TVD). For instance, a conductor casing (not shown)may extend down to about 120 feet TVD, with a diameter of between about28 in. and 60 in. The surface casing 120 may extend down to about 2500feet TVD, with a diameter of between about 22 in. and 48 in. Anintermediate casing (not shown) between the surface casing 120 andproduction casing 122 may extend down to about 8000 feet TVD, with adiameter of between about 16 in. and 36 in. The production casing 122may extend inclinedly (e.g., to case the horizontal portion 110) with adiameter of between about 11 in. and 22 in. The foregoing dimensions aremerely provided as examples and other dimensions (e.g., diameters, TVDs,lengths) are contemplated by the present disclosure. For example,diameters and TVDs may depend on the particular geological compositionof one or more of the multiple subterranean layers (112, 114, 116, and118), particular drilling techniques, as well as a size, shape, ordesign of a hazardous material canister 126 that contains hazardousmaterial to be deposited in the hazardous material storage repositorysystem 100. In some alternative examples, the production casing 122 (orother casing in the drillhole 104) could be circular in cross-section,elliptical in cross-section, or some other shape.

As illustrated, the vertical portion 106 of the drillhole 104 extendsthrough subterranean layers 112, 114, and 116, and, in this example,lands in a subterranean layer 118. As discussed above, the surface layer112 may or may not include mobile water. In this example, a mobile waterlayer 114 is below the surface layer 112 (although surface layer 112 mayalso include one or more sources of mobile water or liquid). Forinstance, mobile water layer 114 may include one or more sources ofmobile water, such as freshwater aquifers, salt water or brine, or othersource of mobile water. In this example of hazardous material storagerepository system 100, mobile water may be water that moves through asubterranean layer based on a pressure differential across all or a partof the subterranean layer. For example, the mobile water layer 114 maybe a permeable geologic formation in which water freely moves (e.g., dueto pressure differences or otherwise) within the layer 114. In someaspects, the mobile water layer 114 may be a primary source ofhuman-consumable water in a particular geographic area. Examples of rockformations of which the mobile water layer 114 may be composed includeporous sandstones and limestones, among other formations.

Other illustrated layers, such as the impermeable layer 116 and thestorage layer 118, may include immobile water. Immobile water, in someaspects, is water (e.g., fresh, salt, brine), that is not fit for humanor animal consumption, or both. Immobile water, in some aspects, may bewater that, by its motion through the layers 116 or 118 (or both),cannot reach the mobile water layer 114, terranean surface 102, or both,within 10,000 years or more (such as to 1,000,000 years).

Below the mobile water layer 114, in this example implementation ofhazardous material storage repository system 100, is an impermeablelayer 116. The impermeable layer 116, in this example, may not allowmobile water to pass through. Thus, relative to the mobile water layer114, the impermeable layer 116 may have low permeability, e.g., on theorder of nanodarcy permeability. Additionally, in this example, theimpermeable layer 116 may be a relatively non-ductile (i.e., brittle)geologic formation. One measure of non-ductility is brittleness, whichis the ratio of compressive stress to tensile strength. In someexamples, the brittleness of the impermeable layer 116 may be betweenabout 20 MPa and 40 MPa.

As shown in this example, the impermeable layer 116 is shallower (e.g.,closer to the terranean surface 102) than the storage layer 118. In thisexample rock formations of which the impermeable layer 116 may becomposed include, for example, certain kinds of sandstone, mudstone,clay, and slate that exhibit permeability and brittleness properties asdescribed above. In alternative examples, the impermeable layer 116 maybe deeper (e.g., further from the terranean surface 102) than thestorage layer 118. In such alternative examples, the impermeable layer116 may be composed of an igneous rock, such as granite.

Below the impermeable layer 116 is the storage layer 118. The storagelayer 118, in this example, may be chosen as the landing for thehorizontal portion 110, which stores the hazardous material, for severalreasons. Relative to the impermeable layer 116 or other layers, thestorage layer 118 may be thick, e.g., between about 100 and 200 feet oftotal vertical thickness. Thickness of the storage layer 118 may allowfor easier landing and directional drilling, thereby allowing thehorizontal portion 110 to be readily emplaced within the storage layer118 during constructions (e.g., drilling). If formed through anapproximate horizontal center of the storage layer 118, the horizontalportion 110 may be surrounded by about 50 to 100 feet of the geologicformation that comprises the storage layer 118. Further, the storagelayer 118 may also have only immobile water, e.g., due to a very lowpermeability of the layer 118 (e.g., on the order of milli- ornanodarcys). In addition, the storage layer 118 may have sufficientductility, such that a brittleness of the rock formation that comprisesthe layer 118 is between about 3 MPa and 10 MPa. Examples of rockformations of which the storage layer 118 may be composed include: shaleand anhydrite. Further, in some aspects, hazardous material may bestored below the storage layer, even in a permeable formation such assandstone or limestone, if the storage layer is of sufficient geologicproperties to isolate the permeable layer from the mobile water layer114.

In some examples implementations of the hazardous material storagerepository system 100, the storage layer 118 (and/or the impermeablelayer 116) is composed of shale. Shale, in some examples, may haveproperties that fit within those described above for the storage layer118. For example, shale formations may be suitable for a long-termconfinement of hazardous material (e.g., in the hazardous materialcanisters 126), and for their isolation from mobile water layer 114(e.g., aquifers) and the terranean surface 102. Shale formations may befound relatively deep in the Earth, typically 3000 feet or greater, andplaced in isolation below any fresh water aquifers. Other formations mayinclude salt or other impermeable formation layer.

Shale formations (or salt or other impermeable formation layers), forinstance, may include geologic properties that enhance the long-term(e.g., thousands of years) isolation of material. Such properties, forinstance, have been illustrated through the long term storage (e.g.,tens of millions of years) of hydrocarbon fluids (e.g., gas, liquid,mixed phase fluid) without escape of substantial fractions of suchfluids into surrounding layers (e.g., mobile water layer 114). Indeed,shale has been shown to hold natural gas for millions of years or more,giving it a proven capability for long-term storage of hazardousmaterial. Example shale formations (e.g., Marcellus, Eagle Ford,Barnett, and otherwise) has stratification that contains many redundantsealing layers that have been effective in preventing movement of water,oil, and gas for millions of years, lacks mobile water, and can beexpected (e.g., based on geological considerations) to seal hazardousmaterial (e.g., fluids or solids) for thousands of years after deposit.

In some aspects, the formation of the storage layer 118 and/or theimpermeable layer 116 may form a leakage barrier, or barrier layer tofluid leakage that may be determined, at least in part, by the evidenceof the storage capacity of the layer for hydrocarbons or other fluids(e.g., carbon dioxide) for hundreds of years, thousands of years, tensof thousands of years, hundreds of thousands of years, or even millionsof years. For example, the barrier layer of the storage layer 118 and/orimpermeable layer 116 may be defined by a time constant for leakage ofthe hazardous material more than 10,000 years (such as between about10,000 years and 1,000,000 years) based on such evidence of hydrocarbonor other fluid storage.

Shale (or salt or other impermeable layer) formations may also be at asuitable depth, e.g., between 3000 and 12,000 feet TVD. Such depths aretypically below ground water aquifer (e.g., surface layer 112 and/ormobile water layer 114). Further, the presence of soluble elements inshale, including salt, and the absence of these same elements in aquiferlayers, demonstrates a fluid isolation between shale and the aquiferlayers.

Another particular quality of shale that may advantageously lend itselfto hazardous material storage is its clay content, which, in someaspects, provides a measure of ductility greater than that found inother, impermeable rock formations (e.g., impermeable layer 116). Forexample, shale may be stratified, made up of thinly alternating layersof clays (e.g., between about 20-30% clay by volume) and other minerals.Such a composition may make shale less brittle and, thus lesssusceptible to fracturing (e.g., naturally or otherwise) as compared torock formations in the impermeable layer (e.g., dolomite or otherwise).For example, rock formations in the impermeable layer 116 may havesuitable permeability for the long term storage of hazardous material,but are too brittle and commonly are fractured. Thus, such formationsmay not have sufficient sealing qualities (as evidenced through theirgeologic properties) for the long term storage of hazardous material.

The present disclosure contemplates that there may be many other layersbetween or among the illustrated subterranean layers 112, 114, 116, and118. For example, there may be repeating patterns (e.g., vertically), ofone or more of the mobile water layer 114, impermeable layer 116, andstorage layer 118. Further, in some instances, the storage layer 118 maybe directly adjacent (e.g., vertically) the mobile water layer 114,i.e., without an intervening impermeable layer 116. In some examples,all or portions of the radiussed drillhole 108 and the horizontaldrillhole 110 may be formed below the storage layer 118, such that thestorage layer 118 (e.g., shale or other geologic formation withcharacteristics as described herein) is vertically positioned betweenthe horizontal drillhole 110 and the mobile water layer 114.

In this example, the horizontal portion 110 of the drillhole 104includes a storage area in a distal part of the portion 110 into whichhazardous material may be retrievably placed for long-term storage. Forexample, a work string (e.g., tubing, coiled tubing, wireline, orotherwise) or other downhole conveyance (e.g., tractor) may be movedinto the cased drillhole 104 to place one or more (three shown but theremay be more or less) hazardous material canisters 126 into long term,but in some aspects, retrievable, storage in the portion 110.

Each canister 126 may enclose hazardous material (shown as material145). Such hazardous material, in some examples, may be biological orchemical waste or other biological or chemical hazardous material. Insome examples, the hazardous material may include nuclear material, suchas SNF recovered from a nuclear reactor (e.g., commercial power or testreactor) or military nuclear material. Spent nuclear fuel, in the formof nuclear fuel pellets, may be taken from the reactor and not modified.Nuclear fuel pellet are solid, although they can contain and emit avariety of radioactive gases including tritium (13 year half-life),krypton-85 (10.8 year half-life), and carbon dioxide containing C-14(5730 year half-life). Other hazardous material 145 may include, forexample, radioactive liquid, such as radioactive water from a commercialpower (or other) reactor.

In some aspects, the storage layer 118 should be able to contain anyradioactive output (e.g., gases) within the layer 118, even if suchoutput escapes the canisters 126. For example, the storage layer 118 maybe selected based on diffusion times of radioactive output through thelayer 118. For example, a minimum diffusion time of radioactive outputescaping the storage layer 118 may be set at, for example, fifty times ahalf-life for any particular component of the nuclear fuel pellets.Fifty half-lives as a minimum diffusion time would reduce an amount ofradioactive output by a factor of 1×10¹⁵. As another example, setting aminimum diffusion time to thirty half-lives would reduce an amount ofradioactive output by a factor of one billion.

For example, plutonium-239 is often considered a dangerous waste productin SNF because of its long half-life of 24,100 years. For this isotope,50 half-lives would be 1.2 million years. Plutonium-239 has lowsolubility in water, is not volatile, and as a solid, its diffusion timeis exceedingly small (e.g., many millions of years) through a matrix ofthe rock formation that comprises the illustrated storage layer 118(e.g., shale or other formation). The storage layer 118, for examplecomprised of shale, may offer the capability to have such isolationtimes (e.g., millions of years) as shown by the geological history ofcontaining gaseous hydrocarbons (e.g., methane and otherwise) forseveral million years. In contrast, in conventional nuclear materialstorage methods, there was a danger that some plutonium might dissolvein a layer that comprised mobile ground water upon confinement escape.

In some aspects, the drillhole 104 may be formed for the primary purposeof long-term storage of hazardous materials. In alternative aspects, thedrillhole 104 may have been previously formed for the primary purpose ofhydrocarbon production (e.g., oil, gas). For example, storage layer 118may be a hydrocarbon bearing formation from which hydrocarbons wereproduced into the drillhole 104 and to the terranean surface 102. Insome aspects, the storage layer 118 may have been hydraulicallyfractured prior to hydrocarbon production. Further in some aspects, theproduction casing 122 may have been perforated prior to hydraulicfracturing. In such aspects, the production casing 122 may be patched(e.g., cemented) to repair any holes made from the perforating processprior to a deposit operation of hazardous material. In addition, anycracks or openings in the cement between the casing and the drillholecan also be filled at that time.

As further shown in FIG. 1, a backfill material 140 may be positioned orcirculated into the drillhole 104. In this example, the backfillmaterial 140 surrounds the canisters 126 and may have a level thatextends uphole to at or near a drillhole seal 134 (e.g., permanentpacker, plug, or other seal). In some aspects, the backfill material 140may absorb radioactive energy (e.g., gamma rays or other energy). Insome aspects, the backfill material 140 may have a relatively lowthermal conductivity, thereby acting as an insulator between thecanisters 126 and the casings.

As further shown in FIG. 1, another backfill material 150 may bepositioned or placed within one or more of the canisters 126 to surroundthe hazardous material 145. In some aspects, the backfill material 150may absorb radioactive energy (e.g., gamma rays or other energy). Insome aspects, the backfill material 150 may have a relatively lowthermal conductivity, thereby acting as an insulator between thehazardous material 145 and the canister 126. In some aspects, thebackfill material 150 may also provide a stiffening attribute to thecanister 126, e.g., reducing crushability, deformation, or other damageto the canister 126.

In some aspects, one or more of the previously described components ofthe system 100 may combine to form an engineered barrier of thehazardous waste material repository 100. For example, in some aspects,the engineered barrier is comprised of one, some, or all of thefollowing components: the storage layer 118, the casing 122, thebackfill material 140, the canister 126, the backfill material 150, theseal 134, and the hazardous material 145, itself. In some aspects, oneor more of the engineered barrier components may act (or be engineeredto act) to: prevent or reduce corrosion in the drillhole 104, prevent orreduce escape of the hazardous material 145; reduce or prevent thermaldegradation of one or more of the other components; and other safetymeasures to ensure that the hazardous material 145 does not reach themobile water layer 114 (or surface layer 112, including the terraneansurface 102).

FIG. 2 is a schematic illustration of an example implementation of ahazardous material storage repository system 200, e.g., a subterraneanlocation for the long-term (e.g., tens, hundreds, or thousands of yearsor more), but retrievable, safe and secure storage of hazardousmaterial. In some aspects, one or more components of repository 200 maybe similar to components described in reference to the hazardousmaterial repository 100 (shown with like reference numbers). Forexample, this figure illustrates the example hazardous material storagerepository system 200 once one or more canisters 226 of hazardousmaterial have been deployed in a subterranean formation 118. In thisexample implementation, at least one of the canisters deployed in thesubterranean formation comprises a spherical hazardous material canister226 (three shown in this example).

Each canister 226 may enclose hazardous material (shown as material245). Such hazardous material, in some examples, may be biological orchemical waste or other biological or chemical hazardous material. Insome examples, the hazardous material may include nuclear material, suchas SNF recovered from a nuclear reactor (e.g., commercial power or testreactor) or military nuclear material. Spent nuclear fuel, in the formof nuclear fuel pellets, may be taken from the reactor and not modified.Nuclear fuel pellet are solid, although they can contain and emit avariety of radioactive gases including tritium (13 year half-life),krypton-85 (10.8 year half-life), and carbon dioxide containing C-14(5730 year half-life). Other hazardous material 245 may include, forexample, radioactive liquid, such as radioactive water from a commercialpower (or other) reactor.

As further shown in FIG. 1, a backfill material 140 may be positioned orcirculated into the drillhole 104. In this example, the backfillmaterial 140 surrounds the canisters 126 and may have a level thatextends uphole to at or near a drillhole seal 134 (e.g., permanentpacker, plug, or other seal). In some aspects, the backfill material 140may absorb radioactive energy (e.g., gamma rays or other energy). Insome aspects, the backfill material 140 may have a relatively lowthermal conductivity, thereby acting as an insulator between thecanisters 126 and the casings.

As further shown in FIG. 2, another backfill material 250 may bepositioned or placed within one or more of the canisters 226 to surroundthe hazardous material 245. In some aspects, the backfill material 250may absorb radioactive energy (e.g., gamma rays or other energy). Insome aspects, the backfill material 250 may have a relatively lowthermal conductivity, thereby acting as an insulator between thehazardous material 245 and the canister 226. In some aspects, thebackfill material 250 may also provide a stiffening attribute to thecanister 226, e.g., reducing crushability, deformation, or other damageto the canister 226.

In some aspects, one or more of the previously described components ofthe system 200 may combine to form an engineered barrier of thehazardous waste material repository 200. For example, in some aspects,the engineered barrier is comprised of one, some, or all of thefollowing components: the storage layer 118, the casing 122, thebackfill material 140, the canister 226, the backfill material 250, theseal 134, and the hazardous material 245, itself. In some aspects, oneor more of the engineered barrier components may act (or be engineeredto act) to: prevent or reduce corrosion in the drillhole 104, prevent orreduce escape of the hazardous material 245; reduce or prevent thermaldegradation of one or more of the other components; and other safetymeasures to ensure that the hazardous material 245 does not reach themobile water layer 114 (or surface layer 112, including the terraneansurface 102).

Although described as a spherical canister 226, the canister 226 may besubstantially spherical (e.g., not exactly spherical in exterior shapebut close to spherical). For example, in some aspects, the sphericalcanister 226 may have one or more flat or substantially flat portions(e.g., at opposite poles, such as a globe). In some aspects, thecanister 226 may be exactly spherical.

The spherical canister 226 may be deployed into the drillhole 104 by,for example, a downhole conveyance (e.g., a tubular conveyance orwireline conveyance). In alternative aspects, the spherical canister 226may be deployed into the drillhole 104 by a downhole tractor. In someaspects, due to the spherical (or substantially spherical) shape of theexterior housing of the canister 226, deployment of the canister 226into the drillhole 104 may also include rolling the canister 226 throughone or more portions of the drillhole 104. In some aspects, due to thespherical (or substantially spherical) shape of the exterior housing ofthe canister 226, at least a portion of the drillhole 104 (e.g., some orall of the substantially horizontal portion 110) may be angledvertically away from the terranean surface 102 so that the canister 226does not move (e.g., by force of gravity) from the portion 110 towardthe substantially vertical portion 106 after deployment.

FIGS. 3A-3D are schematic illustrations of example implementations of aspherical hazardous material canister, such as the spherical hazardousmaterial canister 226 shown in FIG. 2. FIG. 3A shows an exampleimplementation of a spherical canister 300, while FIG. 3B shows anotherexample implementation of a spherical canister 350. Each of canisters300 and 350 may store hazardous material, such as radioactive waste. Insome aspects, the radioactive waste may comprise SNF (e.g., SNF pelletsare at least a portion of a SNF assembly) or high level radioactivewaste. In some aspects, one or both of spherical canisters 300 and 350may be utilized as a spherical hazardous waste canister 226 as shown inthe hazardous waste repository 200 in FIG. 2.

Spherical canister 300 is shown in FIG. 3A and includes a spherical (orsubstantially spherical) housing 302 comprised of a top portion 308 (orcap 308) and a bottom portion 306. Each portion 308 and 306 are at leastpartially hollow such that, when joined, an interior volume 304(represented in dashed line) is defined within the housing 302. Thebottom portion 306 includes an edge 314 that has a dimension (e.g.,circumference) that is substantially similar, if not identical to, adimension (e.g., circumference) of an edge 312 of the top portion 308.As shown in FIG. 3A, hazardous material 310 in the form of SNF (i.e.,nuclear or radioactive waste) is positioned in the interior volume 304of the bottom portion 306 of the housing 302. In some aspects, one orboth of the edges 312 and 314 may be beveled or angled in order to moresealingly mate with the other of the edges.

In example implementations, the canister 300 may be from 4 to 12 inchesin diameter, and made of a corrosion-resistant alloy, such as Alloy-625.In the example of the hazardous material 310 being SNF pellets, the SNFpellets (which, in an assembly for commercial nuclear fuel arecylindrical in shape) are typically 1 cm in diameter, and 1 cm inlength. The SNF pellets are comprised primarily of UO₂ ceramic with adensity of 10 g/cm³. As shown in FIG. 3A, the housing 302 of thespherical canister 300 generally is made of two hemispheres: top portion308 and bottom portion 306. In this example, the bottom portion 306 maybe filled with stacked SNF rods (or portions of such rods). These rodsconsist of small pipes that hold the SNF pellets. Longer fuel rods areused in commercial and defense fuel assemblies and typically made of analloy of zirconium; however, these rods can be made of a differentmaterial. That material could be a corrosion-resistant alloy and/or itcould contain a neutron absorber such as boron to reduce the likelihoodof the fuel configuration reaching criticality. The rods could bestacked in a hexagonal close-packed array.

In an assembly operation of the spherical canister 300, when the bottomportion 306 of the housing 302 is filled with fuel pellets (i.e., thevolume 304 is filled), then the top portion 308 (e.g., the lid) would beplaced on the bottom portion 306, and the two hemispheres joined orsealed (e.g., threadingly, by welding, by adhesive, by mechanicalfasteners, or otherwise) by joining or sealing the edges 312 and 314together. One method for welding might be spin-welding (frictionwelding). The edges 312 and 314 that are welded together could be radialin direction, or they could be canted to provide greater surface areaand to facilitate placement and centering. In an example implementation,the spherical housing 302 is a 4-inch inner diameter sphere that wouldhave volume of 108 cm³ and might hold 80 SNF pellets (allowing forimperfect packing and the volume of the rods). An 8 inch diameter spherehousing 300 could hold about eight times as many SNF pellets.

FIG. 3B shows a spherical canister 350. Spherical canister 350 includesa spherical (or substantially spherical) housing 352 comprised of a lid358 and a bottom portion 356. In contrast to the canister 300, thebottom portion 356 of the canister 350 defines all or most of aninterior volume 354, while the lid 358 simply seals a small portion ofthe housing 352. Thus, the canister 350, instead of having twohemispherical portions of substantially similar size, includes a lid 358that is smaller (and possibly much smaller) than the bottom portion 356.When joined, the interior volume 354 (represented in dashed line) isdefined within the housing 352. The bottom portion 356 includes an edge360 formed in a surface of the bottom portion 356 that has a dimension(e.g., circumference) that is substantially similar, if not identicalto, a dimension (e.g., circumference) of an edge 362 of the lid 358.Although not specifically shown in FIG. 3B, hazardous material (such asmaterial 310) in the form of SNF (i.e., nuclear or radioactive waste) ispositionable in the interior volume 354 of the bottom portion 356 of thehousing 352. In some aspects, one or both of the edges 360 and 362 maybe beveled or angled in order to more sealingly mate with the other ofthe edges.

In example implementations, the canister 350 may be from 4 to 12 inchesin diameter, and made of a corrosion-resistant alloy, such as Alloy-625.In the example of the hazardous material being SNF pellets, the SNFpellets (which, in an assembly for commercial nuclear fuel arecylindrical in shape) are typically 1 cm in diameter, and 1 cm inlength. The SNF pellets are comprised primarily of UO₂ ceramic with adensity of 10 g/cm³. In this example, the bottom portion 356 may befilled with stacked SNF rods (or portions of such rods). These rodsconsist of small pipes that hold the SNF pellets. Longer fuel rods areused in commercial and defense fuel assemblies and typically made of analloy of zirconium; however, these rods can be made of a differentmaterial. That material could be a corrosion-resistant alloy and/or itcould contain a neutron absorber such as boron to reduce the likelihoodof the fuel configuration reaching criticality. The rods could bestacked in a hexagonal close-packed array.

In an assembly operation of the spherical canister 350, when the bottomportion 356 of the housing 302, and therefore the interior volume 354,is filled with fuel pellets, then the lid 358 is placed on the bottomportion 356. The lid 358 is then joined or sealed (e.g., threadingly, bywelding, by adhesive, by mechanical fasteners, or otherwise) to thebottom portion 356 by joining or sealing the edges 360 and 362 together.One method for welding might be spin-welding (friction welding). Theedges 360 and 362 that are welded together could be radial in direction,or they could be canted to provide greater surface area and tofacilitate placement and centering. In an example implementation, thespherical housing 352 is a 4-inch inner diameter sphere that would havevolume of 108 cm³ and might hold 80 SNF pellets (allowing for imperfectpacking and the volume of the rods). An 8 inch diameter sphere housing350 could hold about eight times as many SNF pellets.

In some aspects of spherical canister 350, individual SNF pellets may beplaced in the bottom portion 356 without being in rod form (i.e., not asa SNF rod or rod portion). The SNF pellets may fill the bottom portion,and then the lid will be placed on top and welded to the lower section.The lower section might be shaken or vibrated as the pellets fall in toimprove the packing. But the SNF pellets, in this configuration, may notbe necessarily arranged in an orderly fashion.

In some aspects, example spherical canisters 300 and 350 (either orboth) may be crush-resistant. For example, the interior volumes 304and/or 354 may be filled (all or partially, once the hazardous waste isincluded therein) with a fill material that is strong under compression,such as sand. The fill material may also be any solid that is strongunder compression. In an example aspect, the filling material betweenthe SNF (in rod or pellet form) is sand saturated with a gas that helpsconduct heat from the radioactivity of the pellets. That gas could behelium, argon, or nitrogen (as some examples).

Although both canisters 300 and 350 are shown and described as beingspherical or substantially spherical in external shape, other externalshapes are contemplated by the present disclosure. For example, a shapeof the canister 300 or 350 may be a compromise between sphere andcylinder; the shape could be elliptical or cylindrical with roundededges. Although some of the advantages of the spherical shape may becompromised, there can be advantages in handling and filling of acanister that included an elongated external shape.

Turning to FIG. 3C, this figure illustrates another exampleimplementation of a hazardous waste storage system that includes one ormore spherical canisters. FIG. 3C illustrates a cross-section of ahazardous material canister 375 that is deployed in a hazardous materialrepository (a portion of which is shown in FIG. 3C). As shown, thehazardous material canister 375 may be cylindrical or substantiallycylindrical in shape and sized to enclose one or more sphericalcanisters, such as one or more spherical canisters 300 or 350. In someaspects, canister 375 may be used as canister 126 as shown in FIG. 1.The spherical canisters 300 or 350, as shown can be placed inside of thecylindrical canister 375, e.g., to simplify handling of hazardousmaterial. For example, a large number of spherical canisters 300 or 350could be placed inside the canister 375, which, in some aspects, issimilar in shape to a SNF assembly (e.g., a single SNF assembly). Thehazardous material canister 375 may be, e.g., 5 to 12 inches in innerdiameter and 1 to 20 feet long. As shown, the canister 375 is positionedin the substantially horizontal portion 110 of the drillhole 104.

In some aspects, shielding 380 may be positioned at one or both ends ofthe canister 375. In some aspects, the shielding 380 may be attached toor integral with the hazardous material canister 375. The shielding 380may be a radiation shielding (e.g., to reduce or stop gamma radiationfrom escaping the canister 375) or contact shielding (e.g., to reduce oreliminate damage to the canister 375 due to contact from other canistersor objects), or both. In some aspects, the hazardous material canister375 may be made of corrosion-resistant alloy or of some other material.The hazardous material canister 375 may simplify handling and placementof the hazardous material in a deep, human-unoccupiable directionaldrillhole. In addition, the hazardous material canister 375 may providean additional engineered barrier to escape of hazardous material, suchas radioisotopes from SNF. The hazardous material canister 375 may bedesigned to hold a linear array of spherical canisters 300 or 350.Alternatively, the hazardous material canister 375 may be larger andenclose several (e.g., 3) side-by-side linear arrays of sphericalcanisters 300 or 350. In some aspects, multiple linear arrays mayprovide for more efficient use of the volume of the hazardous materialcanister 375 as well as drillhole. In some aspects, space within thehazardous material canister 375 that is not occupied by the one or morespherical canisters 300 or 350 may be filled with a sand-like material,a liquid, or a gas. In some aspects, the hazardous material canister 375includes a frame mounted in its interior volume that holds the sphericalcanisters 300 or 350 in place inside the hazardous material canister375. The hazardous material canister 375, in some aspects, may berectangular in cross-section rather than circular. Other cross-sectionalshapes, such as hexagonal, are also contemplated by the presentdisclosure.

In some aspects, implementations of a hazardous material sphericalcanister according to the present disclosure may provide an additionalmeasure of protection against the unwanted release of hazardous materialstored in a hazardous waste repository in a geographic area thatexperiences seismic events, such as earthquakes. For example, it iswidely believed that underground disposal (e.g., in deep,human-unoccupiable directional drillholes) of nuclear waste (e.g., SNFor high level waste) cannot be done safely in regions in whichearthquakes are likely. Since some nuclear waste is generated in regionsthat have large and frequent earthquakes (e.g., nuclear waste fromcommercial nuclear reactors in California, Taiwan, South Korea, andJapan to name a few), that assumption requires a distant location fordisposal. Distant disposal can create legal issues (some countries aremandated to dispose within the country) and real or perceived risks fromtransportation.

In some aspects, the shaking caused by a nearby earthquake is not theprimary danger to a hazardous material (e.g., nuclear waste) canisterpositioned in a hazardous waste repository of a deep directionaldrillhole formed in a subterranean formation. The reason is that suchaccelerations are typically less than 1 g (i.e., less than 980 gal,where a gal is the standard unit for acceleration, equal to 1 cm persecond per second). Such accelerations present threats to surfacestructures, but nuclear waste canisters are designed to endure muchstronger accelerations.

In some aspects, the greater danger from an earthquake is that a fault(created or caused or moved by the earthquake) will shear through thehazardous waste repository of the drillhole, which in turn can damageone or more nuclear waste canisters positioned in the repository(thereby causing radioactive waste to leak into water in thesubterranean formation. Such canisters, for example, may have a largelength to cross-section ratio (e.g., long and thin, designed to storeone or more SNF assemblies). Such canister, for instance, may storenuclear waste (e.g., SNF) in unmodified fuel assemblies for placement inthe deep directional drillhole. Such fuel assemblies are typically 8 to12 inches in diameter and 14 feet long; the canister to hold anunmodified SNF assembly would be similar in diameter and length. Thus,it is the long and narrow shape of the fuel assembly canisters that maymake them vulnerable to being sheared by an earthquake fault thatcrosses the hazardous waste repository of the drillhole.

As previously described and shown in FIGS. 3A-3C, exampleimplementations of the present disclosure include a nuclear wastecanister that encloses nuclear waste (e.g., SNF or high level waste) forstorage in a deep directional drillhole, where the canister includes aspherical or substantially spherical housing. Such a spherical nuclearwaste canister, in some aspects, may be less susceptible to breakage orleakage in the event of an earthquake that creates a fault that shearsthe hazardous waste repository of the deep directional drillhole. Insome aspects, the nuclear waste, such as a SNF assembly, may berepackaged to fit into the spherical nuclear waste canister.

The example implementations of a canister that is shaped as a smallsphere may be very resistant to shear from an earthquake. The sphericalshape of the housing makes the canister more resistant to crushingcompared to canisters of any other shape. A torque on the sphericalcanister will tend to rotate it rather than to bend it, as would be thecase for a canister whose length and width are unequal.

As also previously described, the spherical canisters can also be placedinside of a longer cylindrical canister, to simplify handling. Forexample, a large number of spherical canisters could be placed inside along outer canister, one that is similar in shape to the original fuelassembly. That canister might be 5 to 12 inches in inner diameter and 1to 20 feet long. The outer canister also provides some protectionagainst shear from earthquakes.

Earthquake faults can have a range of transverse extent, frommillimeters to kilometers. If the boundary is sharp, then there will bea shearing force placed across the spherical canister. Unless the narrowline of the earthquake discontinuity lies exactly in the plane ofsymmetry of the sphere, the shearing force will become, in part, a forcealong the axis of the drillhole, and will force the sphere to move inthat direction, provided that there is space to move. To provide thatspace, gaps may be left between the spherical nuclear waste canisters(or between outer canisters such as canister 375 that encloses multiplespherical canisters and may be filled with a fluid or other materialthat will yield when a force is placed on it). Once the sphericalcanister is more on one side of the drillhole than the other, theshearing force will be greater (as it occurs across the curved part ofthe spherical canister) and it will continue to push the sphericalcanister into the drillhole.

This is illustrated in FIG. 3D. For example, as shown, a fault 390(naturally occurring or due to seismic activity) ruptures 394 anengineered barrier of a hazardous waste repository, such as, forexample, the casing 120 and cement 130 installed in the horizontalportion 110 of the drillhole 104. A force 392 acts on the sphericalcanister (300 or 350). The component of the force on the sphericalcanister 300 or 350 along the axis of the casing 120 pushes thespherical canister 300 or 350 further along in the hazardous wasterepository of the deep directional drillhole and away from the faultline 390. This movement reduces the force 392 on the spherical canister300 or 350 and places the spherical canister 300 or 350 in a locationthat prevents any danger of shearing of the canister (thereby releasinghazardous material).

Although earthquake faults can be very narrow, as shown in FIG. 3D, theycan also be broad and filled with crushed rock or rock that was crushedwhen the fault moved. In such a situation, the forces on the sphericalcanister 300 or 350 may tend to rotate the canister. The advantage of aspherical canister 300 or 350 is that such a canister can rotate withoutchanging an opening in the rock formation in which it is contained inthe repository (e.g., formation 118).

FIG. 4-8 are schematic illustrations of example implementations of ahazardous material canister according to the present disclosure.Although the illustrated implementations of the hazardous materialcanisters are shown as cylindrical or substantially cylindrical inshape, other shapes, such as spherical or substantially spherical,square or rectangular in radial cross-section, or otherwise, are alsocontemplated by the present disclosure. Each example implementation of ahazardous material canister shown in FIGS. 4-8 is designed to store(perhaps permanently) hazardous waste in deep, human-unoccupiabledirectional drillholes (e.g., wellbores). In some aspects, each exampleimplementation of a hazardous material canister shown in FIGS. 4-8 isdesigned to be retrievable from the deep, human-unoccupiable directionaldrillhole to a terranean surface, when needed. The hazardous materialcan be chemical, biological, or, in many examples, radioactive (e.g.,nuclear) in nature. For example, hazardous material may be SNF or highlevel radioactive waste, with either type being in solid, liquid, orgaseous form as stored in the hazardous material canister. In someaspects, each example implementation of a hazardous material canistershown in FIGS. 4-8 is part of an engineered barrier system that preventsthe hazardous material from migrating to a source of ground water orother source of mobile water that can move to consumable water sources.For example, such ground water could dissolve components of the wasteand transport the dissolved radioactive components to the terraneansurface and contaminate human- (or animal-) consumable water.

The nuclear waste emits gamma and X-radiation, making the closeenvironment of the canister dangerous for humans. However, such nuclearwaste needs to be sealed within the canister, such as by welding a topor seal onto the open canister to seal the nuclear waste within a volumeof the canister

For example, FIG. 4 shows an example system 400 for examining andvalidating a weld 408 formed on a hazardous material canister 402, e.g.,to join a cap 406 of the hazardous material canister 402 to a housing404 of the hazardous material canister 402. Conventional methods havebeen used in the past to validate the quality of such welds. Certainmethods are non-destructive. These include visual inspection,ultrasonics, and gamma ray radiography. Radiography typically consistsof putting a source of X-rays or gamma rays near the weld and recordingthe transmitted rays. Any hidden gap or void in the weld would transmitgamma (and/or X-) rays at an increased level.

The example system 400 (and method of operating the system 400) utilizesgamma ray emission (shown as 412) of radioactive (or nuclear) waste 410(e.g., SNF or high level waste) as the source of the radiation used toprobe the weld 408. In some aspects, the term “gamma ray” includes bothgamma rays and X-rays. The gamma rays 412, during inspection of the weld408, may not be viewed directly. However, gamma rays 412 are not onlyabsorbed, but also scattered. That is, a gamma ray hitting the nucleusof an atom, or an electron, can be deflected so that it travels in adifferent direction. This usually involves energy loss of the gamma ray412, but for the present disclosure, the energy loss is small enoughthat the deflected ray is still considered to be a gamma ray 412. Insome aspects, these scattered gamma rays 412 may be used to examine thequality of the weld 408, in particular, whether there are any gaps orvoids 415 within the weld 408 that seals the nuclear waste 410 within avolume 413 defined within the housing 404.

For an example, a flat weld 408 may be formed that connects the canisterhousing 404 with the canister lid 406 (e.g., by spin welding). FIG. 4shows an example implementation of a portion of the hazardous materialcanister 402 in a vertical orientation. The weld 408 may be horizontal,as shown with the dashed lines in FIG. 4. Also, the dashed lines mayshow where the lid 406 of the canister 402 and the housing 404 of thecanister 402 meet (i.e., at the weld 408). In some aspects, a crosssection of the canister 402 taken at the weld 408 is circular. Thus, theweld 408 itself may be a circular weld that joins adjoiningcircumferential edges of the housing 404 and the lid 406 of the canister402. In some aspects, at least one of the housing 404, lid 406, or weld408 are made of a corrosion-resistant alloy, such as Alloy 625.

As shown in FIG. 4, the highly radioactive material 410 is emplaced inthe volume 413 of the canister 402 below the weld 408. The radioactivematerial 410 (e.g., nuclear waste) emits gamma and X-rays (showncollectively as 412) in all directions. The gamma rays of interest arethose that are emitted in a generally upward direction, and which pathscross the weld 408 to be examined.

When the source of gamma rays 412 is sufficiently high, an image of thesource distribution can be obtained by using a gamma ray camera 420 thatincludes a shield 422 (e.g., a lead shield) with one or more openings424. For example, as shown, the shield 422 may have a single smallopening 424 and a gamma ray detector 426 positioned behind the hole 424(e.g., opposite the canister 402). For example, as shown in FIG. 4, thegamma ray, or “pinhole,” camera 420 is positioned so as to receive gammarays 412 that potentially exit the sealed canister 402 through one ormore voids 415 in the welded portion 408, through the pinhole 424, andat the gamma ray image detector 426.

In an alternative aspect, the pinhole 424 may be a horizontal slit. Ahorizontal slit may admit more gamma rays 412, but the slit provides nohorizontal resolution, which is not needed if the goal is to validate athin horizontal weld (such as weld 408). The validation of the weld 408may include testing if the layer of the weld scatters as many gamma rays412 as do the layers of the housing 404 and/or lid 406 (e.g., above theweld 408 or below the weld 408). If the scattering is the same orsubstantially the same, then it indicates that there are no voids 415 inthe weld 408.

In further alternative aspects, the gamma ray camera 420 comprises anAnger camera or a coded aperture camera. For example, as an Angercamera, the gamma ray camera 420 includes a series of holes in a gammaabsorber such as lead.

In this example implementation, the gamma ray camera 420 operates toprovide pinhole imaging of scattered radiation 412; the presence of avoid 415 in the weld 408 creates a region in an image created by thegamma ray image detector 426 with less exposure. Thus, the pinholecamera 420 images any voids 415 as a “dark” region, i.e., one with fewergamma rays 412 being received from the nuclear waste 410 in the canister402.

The pinhole camera 410, as shown, for example, is used in gamma rayradiography of the hazardous material canister 402 in combination withthe stored radioactive waste 410 as the source of the gamma rays 412used to verify the integrity of the weld 408. For example, aspects ofthe present disclosure include the pinhole camera 420 to measurescattered radiation (e.g., gamma rays 412) emitted naturally from withinthe canister 402 (e.g., by the enclosed nuclear waste 410) with no needto add an additional source. Thus, aspects of the present disclosureinclude a source of the gamma rays 412 used to measure or determine anintegrity of the weld 408 that seals nuclear waste 410 in the canister402 that is the nuclear waste 410, itself.

In some aspects, one or both of the nuclear waste canister and the gammaray image detector are rotated during the operation of the detector toreceive scattered gamma rays and generate an image of the received gammarays. Thus, in some aspects, the gamma ray image detector may operate toinspect a complete circumference of the weld as the detector or thecanister (or both) rotates (e.g., around 360 degrees).

A controller, control system, or computing system (e.g., control system900) may be connected to the gamma ray image detector 426 and/or thegamma ray camera 420 to receive images from the detector 426. The imagesshow, for example, the scattered radiation that shows the presence ofany void in the weld 408. Based on the image, the computing system 900may determine an integrity of the weld 408. For example, the computingsystem 900 may determine that the images include portions that showvoids of a particular size that indicates that the weld 408 is notsufficient to seal the radioactive waste 410 in the hazardous materialcanister 402.

Turning to FIG. 5, this figure illustrates an example system 500 forexamining and validating a weld 510 formed on a hazardous materialcanister 502, e.g., to join a cap 506 of the hazardous material canister502 to a housing 504 of the hazardous material canister 502.Conventional methods have been used in the past to validate the qualityof such welds. Certain methods are non-destructive. These include visualinspection, ultrasonics, and gamma ray radiography. Radiographytypically consists of putting a source of X-rays or gamma rays near theweld and recording the transmitted rays. Any hidden gap or void in theweld would transmit gamma (and/or X-) rays at an increased level.

In this example, the canister 502 includes the lid 506, which is sealedto the housing 504 of the canister 502 by a weld 510 (e.g., by spinwelding). For instance, example implementations utilize a spin weldingsystem is used to attach the lid 506 to the housing 504 of FIG. 5 (e.g.,through the technique of spin welding). Further, in some aspects,implementations of FIG. 5 include a shield 512 (lead or other materialthat absorbs gamma rays) that is placed within a volume 511 of thecanister 502 to prevent gamma rays 520 from the radioactive waste 508from reaching one or more gamma ray detectors 530, but low enough thatthe shield 512 does not interfere with the imaging of the weld 510. Ifthe weld 510 is created through spin welding, then a region to beexamined by the gamma ray detectors 530 can be no more than one orseveral millimeters in vertical extent. If this is the case, then theshield 512 may cover most of the canister 502. As another example, ashield made from tungsten or tungsten carbide could be used. The shield512 could also be made of a material such as sand (or tungsten carbide)that is packed in at the top part of the canister 502.

The example system 500 (and method of operating the system 500) utilizesgamma ray emission (shown as 520) of radioactive (or nuclear) waste 508(e.g., SNF or high level waste) as the source of the radiation used toprobe the weld 510. In some aspects, the term “gamma ray” includes bothgamma rays and X-rays.

As shown, a flat weld 510 may be formed that connects the canisterhousing 504 with the canister lid 506 (e.g., by spin welding). FIG. 5shows an example implementation of a portion of the hazardous materialcanister 502 in a vertical orientation. The weld 510 may be horizontal,as shown with the dashed lines in FIG. 5. Also, the dashed lines mayshow where the lid 506 of the canister 502 and the housing 504 of thecanister 502 meet (i.e., at the weld 510). In some aspects, a crosssection of the canister 502 taken at the weld 510 is circular. Thus, theweld 510 itself may be a circular weld that joins adjoiningcircumferential edges of the housing 504 and the lid 506 of the canister502. In some aspects, at least one of the housing 504, lid 506, or weld510 are made of a corrosion-resistant alloy, such as Alloy 625.

As shown in FIG. 5, the highly radioactive material 508 is emplaced inthe volume 511 of the canister 502 below the weld 510. The radioactivematerial 508 (e.g., nuclear waste) emits gamma and X-rays (showncollectively as 520) in all directions. The gamma rays of interest arethose that are emitted in a generally upward direction through anaperture 514 of the shield 512 toward the scatterer 516.

In this example, a scatterer is positioned near or attached to an innersurface of the cap and aligned with the small hole in the shield. Inthis example, gamma ray radiation is caused to scatter by the scattererso that the radiography of the weld is essentially a shadow image.

In this example implementation shown in FIG. 5, the gamma shield 512 isplaced above the nuclear material 508 but below the weld 510. The shield512 reduces upward gamma rays 520, and attenuates the number of gammarays 522 that can travel directly to the gamma ray imaging detector 530from the nuclear material 508. For example, gamma rays 520 emitted bythe nuclear material 508 pass through the aperture 514 in the radialmiddle of the shield 512 and hit a point 518 of the scatterer 516. Theaperture 514 could be open or filled with any material that does notstrongly absorb gamma radiation. The point 518 of the scatterer 516, insome examples, is a small sphere or disk of material that stronglyscatters gamma rays 520 (to scattered gamma rays 522); an example istungsten or tungsten carbide or tungsten carbide cobalt. The gamma rays522 scatter off the point 518 in all directions, which gives thescatterer 516 the effect of being a point source of gamma rays 522. Someof these rays 522 pass through the weld 510 and the parts of thecanister 502 near the weld 510 onto the gamma imaging detector 530(e.g., a piece of film, as is often used for dental X-rays, or an arrayof gamma detectors). A shadow of the weld 510 on the imaging detector530 reveals any gaps or discontinuities (e.g., voids) in the weld 510.The shield 512 may also act to limit the number of gamma rays 520 thatemerge from the lid 506 of the canister 502.

In some aspects, the gamma shield 512 serves other additional purposes.For example, if the canister 502 is placed in an external radiationshield without a lid (as may be done when the canister 502 is sittingabove a directional drillhole prior to being lowered into the hole),then a top of the external radiation shield can be open, since most ofgamma rays 520 in the upward direction is absorbed by the shield 512.Also, the shield 512 may reduce an amount of gamma radiation 520 thattravels directly from the radioactive waste 508 to hit the imagingdevice 530; such direct radiation, if not attenuated, would create abackground “fogging” that could obscure the shadow image. Further, dueto the aperture 514 in the shield 512, gamma rays 520 impinge on thepoint 518 of the scatterer 516 to provide a “point-like” source for theshadow radiography. The shield 512 also absorbs most of the upwardtraveling gamma rays 520, thus providing radiation shielding in theupward direction (e.g., from the volume 511 toward the lid 506).

Continuing with FIG. 5, the shield 512 may also provide an internalradiation shield that may ease handling of the canister 502 and allowsthe weld 510 to be made with a lid 506 that does not have an externalradiation shield attached. Further, the gamma shield 512 is placed belowthe weld 510 and is thus in a relatively low gamma ray environment,which facilities radiography of the weld 510. Further, the shield 512includes the aperture 514 that allows gamma rays 520 to hit the point518 of the scatterer 516 that is positioned at the same or close to sameplanar location as the weld 510. Scattering from this point 518 providesa point-like source of gamma rays 522 for the weld 510, which then canbe examined by using shadow imaging.

In an example operation of the system 500, gamma rays 520 emitted by thenuclear material 508 pass through the aperture 514 in the radial middleof the shield 512 and hit the point 518 of the scatterer 516. The gammarays 522 scatter off the scatterer 516 in all directions, which givesthe scatterer 516 the effect of being a point source of gamma rays 522.Some of these rays 522 pass through the weld 510 onto the gamma imagingdetector 530. The shadow of the weld 510 on the imaging detector 530will reveal any gaps or discontinuities in the weld 510.

When the source of gamma rays 522 is sufficiently high, an image of thesource distribution can be obtained by using a gamma ray camera (such ascamera 420) that includes a shield (e.g., a lead shield) with one ormore openings. For example, as shown for camera 420 (which can be usedin system 500 and includes gamma ray detectors 530), the shield may havea single small opening and gamma ray detector 530 positioned behind thehole (e.g., opposite the canister 502). For example, much like as shownin FIG. 4, a gamma ray, or “pinhole,” camera is positioned so as toreceive gamma rays 522 that potentially exit the sealed canister 502through one or more voids in the welded portion 510, through thepinhole, and at the gamma ray image detector 530.

The validation of the weld 510 may include testing if the layer of theweld scatters as many gamma rays 522 as do the layers of the housing 504and/or lid 506 (e.g., above the weld 510 or below the weld 510). If thescattering is the same or substantially the same, then it indicates thatthere are no voids in the weld 510.

In some aspects, one or both of the hazardous material canister 502 andthe gamma ray image detector 530 are rotated during the operation of thedetector 530 to receive scattered gamma rays 522 and generate an imageof the received gamma rays 522. Thus, in some aspects, the gamma rayimage detector 530 may operate to inspect a complete circumference ofthe weld 510 as the detector 530 or the canister 502 (or both) rotates(e.g., around 360 degrees). A controller, control system, or computingsystem (e.g., control system 900) may be connected to the gamma rayimage detector 530 and/or a gamma ray camera to receive images from thedetector 530. The images show, for example, the scattered radiation thatshows the presence of any void in the weld 510. Based on the image, thecomputing system 900 may determine an integrity of the weld 510. Forexample, the computing system 900 may determine that the images includeportions that show voids of a particular size that indicates that theweld 510 is not sufficient to seal the radioactive waste 508 in thehazardous material canister 502.

Turning to FIG. 6, this figure illustrates an example system 600 forexamining and validating a weld 610 formed on a hazardous materialcanister 602, e.g., to join a cap 606 of the hazardous material canister602 to a housing 604 of the hazardous material canister 602.Conventional methods have been used in the past to validate the qualityof such welds. Certain methods are non-destructive. These include visualinspection, ultrasonics, and gamma ray radiography. Radiographytypically consists of putting a source of X-rays or gamma rays near theweld and recording the transmitted rays. Any hidden gap or void in theweld would transmit gamma (and/or X-) rays at an increased level.

In this example, the canister 602 includes the lid 606, which is sealedto the housing 604 of the canister 602 by a weld 610 (e.g., by spinwelding). For instance, example implementations utilize a spin weldingsystem is used to attach the lid 606 to the housing 604 of FIG. 6 (e.g.,through the technique of spin welding). Further, as shown, the hazardousmaterial canister 602 includes a gamma ray source 618 located within avolume 611 of the canister 602 to create gamma rays 622 that passthrough the weld 610 in a gamma ray radiography analysis. In someaspects, the gamma ray source 618 is a radioactive material (that is inaddition to the radioactive nuclear waste 608 disposed in the canister602) in a particular location within the volume 611 of the canister 602.In some aspects, the particular location of the radioactive material 618may be centered in the inner volume 611 of the canister 602 near the lid606 of the canister 602 (as shown in FIG. 6). In some situations, havingthe radioactive source 618 internal to, rather than external of, thecanister 602, can have substantial handling and safety advantages.

In some aspects, the radioactive material 618 may be connected to asupport 616 that is, in turn, connected to the lid 606 (or other part ofthe canister 602). The radioactive material 618, in some aspects, may beamericium-241 (Am-241) that can be used to generate gamma rays 622 thatare then utilized to inspect and validate the quality of the weld 610 orother material (e.g., a corrosion-resistant alloy such as Alloy 625placed by three-dimensional (3D) printing) that attaches the lid 606 tothe housing 604 of the canister 602.

As shown in FIG. 6, the radioactive material 618 may be a physicallysmall (but, in some aspects, highly radioactive) source on a radialcenterline axis of the canister 602 at the same vertical level (asshown, the is canister oriented vertically) as the lid/canister seal(i.e., the weld 610 shown by a dotted line in this figure). As noted,one example source may be americium-241, which has a half-life of 4.6years. This relatively short half-life means that the radioactivematerial 618 can be small and yet emit a large rate of gamma rays 622.Americium-241 also emits a relatively low energy 59.5 keV gamma ray.This low energy is well-matched to the need to examine a relatively thin(e.g., 0.5 cm) canister weld 610. Many other gamma sources could beused, including Co-60, Cs-137, Ba-137, Ir-192, and Na-22.

An example of placement of the gamma source is shown in FIG. 6. In thisfigure, the canister 602 is shown with a radial axis of symmetry 613(shown with a dashed line) in a vertical orientation. The small Am-241gamma source 618 is attached (e.g., permanently) to the lid 606 of thecanister 602 prior to welding (or sealing). The source 618 may be heldin place by a support structure 616. In FIG. 6, the support structure616 is a narrow rod but can also be a larger cylinder or other shape. Inan example implementation, the source 618 is positioned in the sameradial plane of the weld 610, although it could be at a differentlocation.

In an example operation of the system 600, gamma rays 622 emitted by theradioactive source 618 scatter in all directions. Some of these rays 622pass through the weld 610 onto a gamma ray image detector 630 (e.g., asan array of detectors as part of a gamma ray camera) and/or a singlegamma ray image detector 632 (also as part of a gamma ray camera). Theshadow of the weld 610 on the imaging detector 630 will reveal any gapsor discontinuities in the weld 610. An image of the source distributioncan be obtained by using a gamma ray camera (such as camera 420) thatincludes a shield (e.g., a lead shield) with one or more openings. Forexample, as shown for camera 420 (which can be used in system 600 andincludes gamma ray detectors 630), the shield may have a single smallopening and gamma ray detector 630 positioned behind the hole (e.g.,opposite the canister 602). For example, much like as shown in FIG. 4, agamma ray, or “pinhole,” camera is positioned so as to receive gammarays 622 that potentially exit the sealed canister 602 through one ormore voids in the welded portion 610, through the pinhole, and at thegamma ray image detector 630.

The validation of the weld 610 may include testing if the layer of theweld scatters as many gamma rays 622 as do the layers of the housing 604and/or lid 606 (e.g., above the weld 610 or below the weld 610). If thescattering is the same or substantially the same, then it indicates thatthere are no voids in the weld 610.

In some aspects, one or both of the hazardous material canister 602 andthe gamma ray image detector 630 are rotated during the operation of thedetector 630 to receive gamma rays 622 and generate an image of thereceived gamma rays 622. Thus, in some aspects, the gamma ray imagedetector 630 may operate to inspect a complete circumference of the weld610 as the detector 630 or the canister 602 (or both) rotates (e.g.,around 360 degrees). A controller, control system, or computing system(e.g., control system 900) may be connected to the gamma ray imagedetector 630 and/or a gamma ray camera to receive images from thedetector 630. The images show, for example, the scattered radiation thatshows the presence of any void in the weld 610. Based on the image, thecomputing system 900 may determine an integrity of the weld 610. Forexample, the computing system 900 may determine that the images includeportions that show voids of a particular size that indicates that theweld 610 is not sufficient to seal the radioactive waste 608 in thehazardous material canister 602.

In aspects that utilize a moving gamma detector (630 or 632), the motionmay be relative (i.e., not absolute). In some aspects, therefore, thecanister 602 may be rotated rather than the detector 630. If the singlegamma ray detector 632 is utilized, and the radioactive source 618 actsas a point source, then only one point on the canister 602 will beimaged at any one time. If the detector 632 is extended in thehorizontal direction then a horizontal section of the canister 602 canbe observed.

In some aspects, the gamma ray detector 632 (or detectors 630) maydetermine the energy of the observed gamma rays 622. If this is done,then extraneous gammas (from, for example, the nuclear waste 608) can bediscriminated against. For example, while not shown in the FIG. 6, ashield (lead or other material that absorbs gamma rays) can be placedaround the housing 604 of the canister 602 to prevent gamma rays fromthe nuclear waste 608 from reaching the detectors 630 (or 632). Anyshield placed around the housing 604, however, would be low enough suchthat the shield does not interfere with the imaging of the weld 610(i.e., interfere with gamma rays 622 from the radioactive source 618).If the weld 610 is created through spin welding, then the region to beexamined may be no more than one or several millimeters in verticalextent. If this is the case, then the shielding may cover most of thehousing 604 of the canister 602. As another example, a shield made fromtungsten or tungsten carbide could be used. The shield could also bemade of a material such as sand (or tungsten carbide) that is packed inat the top part of the canister 602.

In an alternative implementation, the radioactive source 618 may be aflat, thin disk located at the same or similar vertical height (andradial plane) as the weld 610. This thin disk provides a shadow withvariating resolution; the highest resolution would be at the height ofthe weld 610. Any void at the weld height may be observed with no needfor de-blurring. This alternative configuration offers the capability ofmaximum resolution at the desired inspection location, while allowing amore intense (i.e., larger) radioactive source 618 to be used.

A controller, control system, or computing system (e.g., control system900) may be connected to the gamma ray image detector 630 and/or a gammaray camera to receive images from the detector 630. The images show, forexample, the scattered radiation that shows the presence of any void inthe weld 610. Based on the image, the computing system 900 may determinean integrity of the weld 610. For example, the computing system 900 maydetermine that the images include portions that show voids of aparticular size that indicates that the weld 610 is not sufficient toseal the radioactive waste 608 in the hazardous material canister 602.

Turning to FIG. 7, this figure shows an example implementation of asystem 700 for sealing a hazardous material canister 702 by welding, andmore specifically, spin welding, a lid 706 of the canister 702 to ahousing 704 of the canister 702. As shown in this exampleimplementation, radioactive waste (or material) 708, e.g., nuclear waste708, is emplaced in a volume 710 of the housing 704 of the hazardousmaterial canister 702. The nuclear waste 708, in some aspects, includesSNF (such as a SNF assembly or portion thereof) or high level waste. Forinstance, after SNF or high level waste is loaded into the hazardousmaterial canister 702, the canister 702 must be closed and sealed inorder to prevent any potential leakage paths or radioactive waste leaksfrom the radioactive waste 708. Further, possible pathways that couldspeed a corrosion path from the outside to the volume 710 of thecanister 702 should be avoided. In some aspects, the lid 706 to thecanister 702 is welded in place to seal the SNF (or high level nuclearwaste) within the canister 702. The weld should be of high quality andoffer protection against corrosion that is equally as good as that ofthe material of the canister 702 (e.g., a corrosion resistant alloy suchas CRA 625). In some aspects, welding is very difficult to achieve in ahigh radiation environment. The canister 702 contains radioactivematerial 708 that emits high fluxes of gamma rays and X rays(collectively, “gamma rays”). In some aspects, the weld must satisfy thestringent criteria of the Nuclear Regulatory Commission. The weld isinspected to assure that it has this quality.

The system 700 of FIG. 7 (and methods performed by or with the system700) seals the hazardous material canister 702 through the preparationof the housing 704 and the lid 706 and the application of spin (orfriction) welding the lid 706 onto the housing 704 of the canister 702into which the nuclear waste 708 is enclosed and then sealed (e.g., bythe spin welding of the lid 706 onto the housing 704). An exampleimplementation is shown in FIG. 7, which includes a cross-sectional view(vertical) of the canister housing 704, the lid 706, and a flywheel 722,which may be used in some aspects to rotate or oscillate the lid 706about an axis of rotation 724 during the welding process. The flywheel722 and an optional shield 720 may be part of a spin welding system usedto attach the lid 706 to the housing 704 of FIG. 7.

For example, in some aspects, an open edge 711 of the housing 704 (e.g.,the circumferential edge 711 of the housing 704 of the canister 702 inthe case of a cylindrical housing) is polished to make a flat and cleansurface. A circumferential edge 707 of the lid 706 is similarlyprepared. The lid 706 is then pressed onto the housing 704 (at the openedge 711) and rotated (or in alternative implementations, oscillated).Friction generated between the two circumferential edges 711 and 707 (ofthe housing 704 and the lid 706) creates a weld 713. In some aspects, noadditional metal needs be added to form the weld 713.

In an example operation, the canister 702 is set vertically with theflat polished end 711 facing upward. The lid 706 is placed verticallyabove the open housing 704 of the canister 702 after the nuclear waste708 has been inserted and held tightly by, e.g., the flywheel 722, andmade to spin. The lid 706 and flywheel 722 would then be lowered to makecontact between the lid 706 and the top circumferential edge 711 of thehousing 704. The flywheel 722 could be released, so that the weight ofthe flywheel 722 would press the two polished surfaces 711 and 707together. Friction causes the flywheel 722 to gradually slow itsrotation, and simultaneously, the friction heats the polished flatsurfaces 711 and 707 of both the housing 704 and the lid 706, heatingthem to a particular welding temperature (e.g., based on the material ofthe housing 704 and lid 706). When the spin rotational rate decreases tozero, the lid 706 and the canister 702 are welded together. Then, theflywheel 722 can be removed and the weld 713 is made to sealinglyenclose the nuclear waste 708 within the canister 702.

In some aspects, the polished surfaces 711 and/or 707 may be configuredin opposing male and female surfaces to better create a strong seal withthe weld 713. In some aspects, the polished surfaces 711 and/or 707could be flat on average, but have an undulating up-and-down surface tobetter create a strong seal with the weld 713. As another example, theshield 720 may comprise a gamma ray shield that sits on top of the lid706 (e.g., between the lid 706 and the flywheel 722) to, e.g., aid intransport of the canister 702. The shield 720 may be spun (e.g., by theflywheel 722) during welding or the shield 720 may be attached to thelid 706 after the lid 706 has been welded to the housing 704 of thecanister 702.

Although the system 700 shown in FIG. 7 includes the flywheel 722,alternative implementations do not include the flywheel 722. Forexample, a spin welding system may force the lid 706 onto the housing704 while causing relative motion therebetween to result in friction toenable the weld 713 without the use of the flywheel 722. Further, asnoted, spin motion (e.g., repeated 360° rotation) is also not essential.In some aspects, a back-and-forth oscillation between the lid 706 andthe housing 704 may be utilized to form the weld 713.

In some aspects, the described example operation of the system 700 canbe done remotely without a nearby presence of humans (who would beendangered by the gamma rays). Further, in some aspects, no additionalmaterial (e.g., filler material) is used for the weld 713; only thematerial of which the canister housing 704 and lid 706 is needed tocreate the weld 713. In some aspects, the lid 706 and the housing 704may both be made of corrosion-resistant metal alloys. One such choicefor an alloy would be Alloy-625 (CRA 625). As another example, suchmaterial may facilitate flat, clean surfaces that lead to high qualitywelds with little to no microscopic gaps and voids. As another example,a flat weld between the lid 706 and the canister housing 704 may beparticularly amenable to inspection to verify that the seal is completeand there are not gaps or voids. This can be done either by usinghypersonic probing or by using radiological methods (e.g., as describedwith reference to FIGS. 4-6).

Turning to FIG. 8, this figure shows an example implementation of asystem 800 for sealing a hazardous material canister 802 by sealing ahousing 804 of the canister 802 to enclose radioactive waste 808 withina volume 810 of the canister 802 with a material deposition system 820.As shown in this example implementation, radioactive waste (or material)808, e.g., nuclear waste 808, is emplaced in the volume 810 of thehousing 804 of the hazardous material canister 802. The nuclear waste808, in some aspects, includes SNF (such as a SNF assembly or portionthereof) or high level waste. For instance, after SNF or high levelwaste is loaded into the hazardous material canister 802, the canister802 must be closed and sealed in order to prevent any potential leakagepaths or radioactive waste leaks from the radioactive waste 808.Further, possible pathways that could speed a corrosion path from theoutside to the volume 810 of the canister 802 should be avoided. In someaspects, a cap 806 is formed on and sealed to the housing 804 by the 3Dprinting system 820 to seal the SNF (or high level nuclear waste) withinthe canister 802. The seal should be of high quality and offerprotection against corrosion that is equally as good as that of thematerial of the canister 802 (e.g., a corrosion resistant alloy such asCRA 625). In some aspects, sealing or welding is very difficult toachieve in a high radiation environment. The canister 802 containsradioactive material 808 that emits high fluxes of gamma rays and X rays(collectively, “gamma rays”). In some aspects, the seal must satisfy thestringent criteria of the Nuclear Regulatory Commission. The seal isinspected to assure that it has this quality.

As shown, FIG. 8 shows the example system 800 (and methods performed byor with the system 800) to enclose the nuclear waste 808 in thehazardous material canister 802 by the direct material (e.g., metal)deposition system 820, e.g., a 3D printing system. In some aspects,direct material deposition may have advantages over welding. Thus,described implementations include a method of forming and attaching alid 806 to the housing 804 of the hazardous material canister 802 thatcontains radioactive (or other toxic) material 808. In some aspects, thecanister 802 (e.g., the housing 804 and/or the lid 806) may be made of acorrosion-resistant alloy, such as Alloy-625. Such an alloy can also beused as a material 822 for the direct material deposition system 820.Thus, the system 800 may be used in one or more example operations forbuilding the lid 806 for the canister 802 made in-place (through directmaterial deposition) once the housing 804 has been filed with theradioactive material 808.

In the example system 800 shown in FIG. 8, a sub-lid 812 may be placedon an open end 811 of the housing 804 (through which the nuclear waste808, such as SNF assemblies, is inserted into the volume 810 of thecanister 802). In this example, the sub-lid 812 is also made ofAlloy-625, but it could be made of a different metal (e.g., corrosionresistant alloy or other metal). In some aspects, the sub-lid 812 may bemade of a material that prevents gamma rays from passing therethrough(e.g., a gamma ray shield). In some aspects, the sub-lid 812 may notprovide a seal to the housing 804 by itself, but may provide a platformon which the cap 806 is deposited by the system 820 and formed. Thesub-lid 812, in some aspects, may be relatively thin (as shown) or itcould be thick (e.g., relative to a thickness of the canister housing804 or the lid 806 formed on the canister housing 804 by the directmaterial deposition system 820).

In an example operation of the system 800, the lid 806 is constructed(e.g., to a particular thickness) using the direct material depositionsystem 820. In this example, the direct material deposition system 820may be a 3D printer. For example, a print head of the 3D printer movesover a top surface of the sub-lid 812 and the open end edge 811 of thehousing 804 to deposit material 822 (e.g., corrosion resistant alloydroplets (such as Alloy-625)), which may be liquid or semi-solid. Asshown in FIG. 8, part way through the complete example operation, thelid 806 is partially formed, with a remaining portion 807 of the lid 806shown in dashed line (to be completed). By moving the print head overthese surfaces, the full lid 806 is made and sealed to the housing 804.The lid 806, once formed, seals the nuclear waste 808 in the volume 810of the canister 802.

FIG. 9 is a schematic illustration of an example controller 900 (orcontrol system) according to the present disclosure. For example, thecontroller 900 can be used for the operations described previously, forexample as or as part of a gamma ray detection system as describedherein. For example, the controller 900 may be communicably coupledwith, or as a part of, a gamma ray pinhole camera or gamma ray imagedetector as described herein.

The controller 900 is intended to include various forms of digitalcomputers, such as printed circuit boards (PCB), processors, digitalcircuitry, or otherwise. Additionally the system can include portablestorage media, such as, Universal Serial Bus (USB) flash drives. Forexample, the USB flash drives may store operating systems and otherapplications. The USB flash drives can include input/output components,such as a wireless transmitter or USB connector that may be insertedinto a USB port of another computing device.

The controller 900 includes a processor 910, a memory 920, a storagedevice 930, and an input/output device 940. Each of the components 910,920, 930, and 940 are interconnected using a system bus 950. Theprocessor 910 is capable of processing instructions for execution withinthe controller 900. The processor may be designed using any of a numberof architectures. For example, the processor 910 may be a CISC (ComplexInstruction Set Computers) processor, a RISC (Reduced Instruction SetComputer) processor, or a MISC (Minimal Instruction Set Computer)processor.

In one implementation, the processor 910 is a single-threaded processor.In another implementation, the processor 910 is a multi-threadedprocessor. The processor 910 is capable of processing instructionsstored in the memory 920 or on the storage device 930 to displaygraphical information for a user interface on the input/output device940.

The memory 920 stores information within the controller 900. In oneimplementation, the memory 920 is a computer-readable medium. In oneimplementation, the memory 920 is a volatile memory unit. In anotherimplementation, the memory 920 is a non-volatile memory unit.

The storage device 930 is capable of providing mass storage for thecontroller 900. In one implementation, the storage device 930 is acomputer-readable medium. In various different implementations, thestorage device 930 may be a floppy disk device, a hard disk device, anoptical disk device, a tape device, flash memory, a solid state device(SSD), or a combination thereof.

The input/output device 940 provides input/output operations for thecontroller 900. In one implementation, the input/output device 940includes a keyboard and/or pointing device. In another implementation,the input/output device 940 includes a display unit for displayinggraphical user interfaces.

The features described can be implemented in digital electroniccircuitry, or in computer hardware, firmware, software, or incombinations of them. The apparatus can be implemented in a computerprogram product tangibly embodied in an information carrier, forexample, in a machine-readable storage device for execution by aprogrammable processor; and method steps can be performed by aprogrammable processor executing a program of instructions to performfunctions of the described implementations by operating on input dataand generating output. The described features can be implementedadvantageously in one or more computer programs that are executable on aprogrammable system including at least one programmable processorcoupled to receive data and instructions from, and to transmit data andinstructions to, a data storage system, at least one input device, andat least one output device. A computer program is a set of instructionsthat can be used, directly or indirectly, in a computer to perform acertain activity or bring about a certain result. A computer program canbe written in any form of programming language, including compiled orinterpreted languages, and it can be deployed in any form, including asa stand-alone program or as a module, component, subroutine, or otherunit suitable for use in a computing environment.

Suitable processors for the execution of a program of instructionsinclude, by way of example, both general and special purposemicroprocessors, and the sole processor or one of multiple processors ofany kind of computer. Generally, a processor will receive instructionsand data from a read-only memory or a random access memory or both. Theessential elements of a computer are a processor for executinginstructions and one or more memories for storing instructions and data.Generally, a computer will also include, or be operatively coupled tocommunicate with, one or more mass storage devices for storing datafiles; such devices include magnetic disks, such as internal hard disksand removable disks; magneto-optical disks; and optical disks. Storagedevices suitable for tangibly embodying computer program instructionsand data include all forms of non-volatile memory, including by way ofexample semiconductor memory devices, such as EPROM, EEPROM, solid statedrives (SSDs), and flash memory devices; magnetic disks such as internalhard disks and removable disks; magneto-optical disks; and CD-ROM andDVD-ROM disks. The processor and the memory can be supplemented by, orincorporated in, ASICs (application-specific integrated circuits).

To provide for interaction with a user, the features can be implementedon a computer having a display device such as a CRT (cathode ray tube)or LCD (liquid crystal display) or LED (light-emitting diode) monitorfor displaying information to the user and a keyboard and a pointingdevice such as a mouse or a trackball by which the user can provideinput to the computer. Additionally, such activities can be implementedvia touchscreen flat-panel displays and other appropriate mechanisms.

The features can be implemented in a control system that includes aback-end component, such as a data server, or that includes a middlewarecomponent, such as an application server or an Internet server, or thatincludes a front-end component, such as a client computer having agraphical user interface or an Internet browser, or any combination ofthem. The components of the system can be connected by any form ormedium of digital data communication such as a communication network.Examples of communication networks include a local area network (“LAN”),a wide area network (“WAN”), peer-to-peer networks (having ad-hoc orstatic members), grid computing infrastructures, and the Internet.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyinventions or of what may be claimed, but rather as descriptions offeatures specific to particular implementations of particularinventions. Certain features that are described in this specification inthe context of separate implementations can also be implemented incombination in a single implementation. Conversely, various featuresthat are described in the context of a single implementation can also beimplemented in multiple implementations separately or in any suitablesubcombination. Moreover, although features may be described above asacting in certain combinations and even initially claimed as such, oneor more features from a claimed combination can in some cases be excisedfrom the combination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingmay be advantageous. Moreover, the separation of various systemcomponents in the implementations described above should not beunderstood as requiring such separation in all implementations, and itshould be understood that the described program components and systemscan generally be integrated together in a single software product orpackaged into multiple software products.

A first example implementation according to the present disclosureincludes a nuclear waste canister that includes a spherical orsubstantially spherical outer housing that defines an inner volume; anda storage space defined within the inner volume of the outer housing,the storage space configured to enclose a plurality of portions of thenuclear waste. The outer housing is configured to store nuclear waste ina human-unoccupiable directional drillhole

In an aspect combinable with the first example implementation, thenuclear waste includes spent nuclear fuel.

In another aspect combinable with any of the previous aspects of thefirst example implementation, the portions of the nuclear waste includespent nuclear fuel pellets.

In another aspect combinable with any of the previous aspects of thefirst example implementation, the outer housing includes a corrosionresistant alloy.

In another aspect combinable with any of the previous aspects of thefirst example implementation, the corrosion resistant alloy includes CRA625.

In another aspect combinable with any of the previous aspects of thefirst example implementation, the outer housing includes a first portionand a second portion.

In another aspect combinable with any of the previous aspects of thefirst example implementation, each of the first and second portions ofthe outer housing includes a hemispherical portion.

In another aspect combinable with any of the previous aspects of thefirst example implementation, herein the hemispherical portions areconfigured to weld together to form the outer housing.

In another aspect combinable with any of the previous aspects of thefirst example implementation, the first portion includes a semisphericalportion that includes a hole and the second portion includes a lid sizedto fit the hole.

In another aspect combinable with any of the previous aspects of thefirst example implementation, semispherical portion and the lid areconfigured to weld together to form the outer housing.

Another aspect combinable with any of the previous aspects of the firstexample implementation further includes a plurality of rods positionedin the storage space, each of the rods configured to hold a plurality ofspent nuclear fuel pellets.

In another aspect combinable with any of the previous aspects of thefirst example implementation, each rod is made from a corrosionresistant material or a neutron absorbing material.

A second example implementation includes a method for containing nuclearwaste that includes placing a plurality of portions of nuclear waste ina storage space of an inner volume of a spherical or substantiallyspherical outer housing of a nuclear waste canister; and sealing thenuclear waste canister to enclose the plurality of portions of nuclearwaste in the inner volume.

An aspect combinable with the second example implementation furtherincludes moving the sealed nuclear waste canister into a hazardous wasterepository of a human-unoccupiable directional drillhole formed in asubterranean formation.

In another aspect combinable with any of the previous aspects of thesecond example implementation, the nuclear waste includes spent nuclearfuel.

In another aspect combinable with any of the previous aspects of thesecond example implementation, the portions of the nuclear waste includespent nuclear fuel pellets.

In another aspect combinable with any of the previous aspects of thesecond example implementation, the outer housing includes a corrosionresistant alloy.

In another aspect combinable with any of the previous aspects of thesecond example implementation, the corrosion resistant alloy includesCRA 625.

In another aspect combinable with any of the previous aspects of thesecond example implementation, the outer housing includes a firstportion and a second portion.

In another aspect combinable with any of the previous aspects of thesecond example implementation, each of the first and second portions ofthe outer housing includes a hemispherical portion.

Another aspect combinable with any of the previous aspects of the secondexample implementation further includes welding the hemisphericalportions together to form the outer housing.

In another aspect combinable with any of the previous aspects of thesecond example implementation, the first portion includes asemispherical portion that includes a hole and the second portionincludes a lid sized to fit the hole.

Another aspect combinable with any of the previous aspects of the secondexample implementation further includes welding the semisphericalportion and the lid together to form the outer housing.

Another aspect combinable with any of the previous aspects of the secondexample implementation further includes inserting a plurality of spentnuclear fuel pellets into a plurality of rods positioned in the storagespace.

In another aspect combinable with any of the previous aspects of thesecond example implementation, each rod is made from a corrosionresistant material or a neutron absorbing material.

A third example implementation includes a nuclear waste storage systemthat includes a cylindrical nuclear waste container that defines aninner space; and a plurality of nuclear waste canisters according to anyof the aspects of the first example implementation positioned in theinner space of the nuclear waste container.

In an aspect combinable with the third example implementation, thenuclear waste container includes radiation shielding at a firstproximate end and a second distal end of the container.

A fourth example implementation includes a method for inspecting a weldof a nuclear waste canister that includes positioning a gamma ray imagedetector near a nuclear waste canister that encloses nuclear waste. Thenuclear waste canister includes a housing that includes a volume inwhich the waste is enclosed and a cap connected to the housing with atleast one weld to seal the nuclear waste in the nuclear waste canister.The method further includes receiving, at the gamma ray image detector,gamma rays from the nuclear waste that travel from the nuclear waste,through a hole in a gamma ray shield that is positioned in the volume tohit a scatterer positioned above the shield, scattered toward the weld,and through one or more voids in the weld; generating an image of thereceived gamma rays with the gamma ray image detector; and based on thegenerated image, determining an integrity of the at least one weld.

In an aspect combinable with the fourth example implementation, thenuclear waste includes spent nuclear fuel.

In an aspect combinable with any of the previous aspects of the fourthexample implementation, the spent nuclear fuel includes at least onespent nuclear fuel assembly.

In an aspect combinable with any of the previous aspects of the fourthexample implementation, the gamma ray image detector includes a pinholecamera.

In an aspect combinable with any of the previous aspects of the fourthexample implementation, at least one of the housing, the cap, or a weldmaterial includes a corrosion resistant alloy.

In an aspect combinable with any of the previous aspects of the fourthexample implementation, each of the housing, the cap, and the weldmaterial includes the corrosion resistant alloy.

In an aspect combinable with any of the previous aspects of the fourthexample implementation, the corrosion resistant alloy includes CRA 625.

In an aspect combinable with any of the previous aspects of the fourthexample implementation, the at least one weld includes a horizontalweld.

In an aspect combinable with any of the previous aspects of the fourthexample implementation, the hole in the gamma ray shield is radiallyaligned with a centerline axis of the housing.

In an aspect combinable with any of the previous aspects of the fourthexample implementation, the hole in the gamma ray shield and thescatterer are radially aligned with a centerline axis of the housing.

An aspect combinable with any of the previous aspects of the fourthexample implementation further includes rotating at least one of thenuclear waste canister or the gamma ray image detector during thereceiving, at the gamma ray image detector, of the gamma rays from thenuclear waste that travel through the one or more voids in the weld.

In an aspect combinable with any of the previous aspects of the fourthexample implementation, the rotating includes rotating at least one ofthe nuclear waste canister or the gamma ray image detector for 360degrees.

In an aspect combinable with any of the previous aspects of the fourthexample implementation, the cap is spin welded to the housing.

A fifth example implementation includes a system for inspecting a weldof a nuclear waste canister that includes a nuclear waste canister and agamma ray image detector system. The nuclear waste canister enclosesnuclear waste and includes a housing that includes a volume configuredto enclose the nuclear waste, a cap connected to the housing with atleast one weld to seal the nuclear waste in the nuclear waste canister,a gamma ray shield that is positioned in the volume between the nuclearwaste and the cap, and a scatterer positioned above the shield. Thegamma ray image detector system is positionable adjacent the nuclearwaste canister and configured to receive gamma rays from the nuclearwaste that travel through a hole in the gamma ray shield to hit thescatterer to scatter toward the weld and travel through one or morevoids in the weld, generate an image of the received gamma rays, andbased on the generated image, determine an integrity of the at least oneweld.

In an aspect combinable with the fifth example implementation, thenuclear waste includes spent nuclear fuel.

In an aspect combinable with any of the previous aspects of the fifthexample implementation, the spent nuclear fuel includes at least onespent nuclear fuel assembly.

In an aspect combinable with any of the previous aspects of the fifthexample implementation, wherein the gamma ray image detector includes apinhole camera.

In an aspect combinable with any of the previous aspects of the fifthexample implementation, at least one of the housing, the cap, or a weldmaterial includes a corrosion resistant alloy.

In an aspect combinable with any of the previous aspects of the fifthexample implementation, each of the housing, the cap, and the weldmaterial includes the corrosion resistant alloy.

In an aspect combinable with any of the previous aspects of the fifthexample implementation, the corrosion resistant alloy includes CRA 625.

In an aspect combinable with any of the previous aspects of the fifthexample implementation, the at least one weld includes a horizontalweld.

In an aspect combinable with any of the previous aspects of the fifthexample implementation, the hole in the gamma ray shield is radiallyaligned with a centerline axis of the housing.

In an aspect combinable with any of the previous aspects of the fifthexample implementation, the hole in the gamma ray shield and thescatterer are radially aligned with a centerline axis of the housing.

In an aspect combinable with any of the previous aspects of the fifthexample implementation, at least one of the nuclear waste canister orthe gamma ray image detector is configured to rotate during thereceiving, at the gamma ray image detector, of the gamma rays from thenuclear waste that travel through the one or more voids in the weld.

In an aspect combinable with any of the previous aspects of the fifthexample implementation, the rotation includes 360 degrees.

In an aspect combinable with any of the previous aspects of the fifthexample implementation, the cap is spin welded to the housing.

A sixth example implementation includes a method for inspecting a weldof a nuclear waste canister that includes positioning a gamma ray imagedetector near a nuclear waste canister that encloses nuclear waste. Thenuclear waste canister includes a housing that includes a volume inwhich the nuclear waste and a gamma ray source material are enclosed anda top connected to the housing with at least one weld to seal thenuclear waste in the nuclear waste canister. The method further includesreceiving, at the gamma ray image detector, gamma rays from the gammaray source material that travel through one or more voids in the weld;generating an image of the received gamma rays with the gamma ray imagedetector; and based on the generated image, determining an integrity ofthe at least one weld.

In an aspect combinable with the sixth example implementation, thenuclear waste includes spent nuclear fuel.

In an aspect combinable with any of the previous aspects of the sixthexample implementation, the spent nuclear fuel includes at least onespent nuclear fuel assembly.

In an aspect combinable with any of the previous aspects of the sixthexample implementation, the gamma ray source material includesAmericium-241.

In an aspect combinable with any of the previous aspects of the sixthexample implementation, the gamma ray source material is positioned at avertical location in the volume of the canister to vertically align withthe at least one weld.

In an aspect combinable with any of the previous aspects of the sixthexample implementation, the gamma ray source material is positioned ator near a radial centerline of the volume of the canister.

In an aspect combinable with any of the previous aspects of the sixthexample implementation, each of the housing, the top, and the weldmaterial includes the corrosion resistant alloy.

In an aspect combinable with any of the previous aspects of the sixthexample implementation, the corrosion resistant alloy includes CRA 625.

In an aspect combinable with any of the previous aspects of the sixthexample implementation, the at least one weld includes a horizontalweld.

In an aspect combinable with any of the previous aspects of the sixthexample implementation, receiving the gamma rays includes receiving aplurality of gamma rays that emit from the gamma ray source material andscatter through the volume of the nuclear waste container and throughone or more voids in the one or more welds toward the gamma ray imagedetector.

An aspect combinable with any of the previous aspects of the sixthexample implementation further includes rotating at least one of thenuclear waste canister or the gamma ray image detector during thereceiving, at the gamma ray image detector, of the gamma rays from thegamma ray source material that travel through the one or more voids inthe weld.

In an aspect combinable with any of the previous aspects of the sixthexample implementation, the rotating includes rotating at least one ofthe nuclear waste canister or the gamma ray image detector for 360degrees.

In an aspect combinable with any of the previous aspects of the sixthexample implementation, the nuclear waste canister further includes agamma ray shield positioned in the volume and vertically between thenuclear waste and the gamma ray source material.

In an aspect combinable with any of the previous aspects of the sixthexample implementation, the gamma ray shield is positioned verticallybetween the at least one weld and the nuclear waste.

A seventh example implementation includes a system for inspecting a weldof a nuclear waste canister that includes a nuclear waste canister thatencloses nuclear waste and includes a housing that includes a volumeconfigured to enclose the nuclear waste and a top connected to thehousing with at least one weld to seal the nuclear waste in the nuclearwaste canister. The system further includes a gamma ray source materialpositioned in the volume of the housing; and a gamma ray image detectorsystem positionable adjacent the nuclear waste canister and configuredto receive gamma rays from the gamma ray source material that travelthrough one or more voids in the weld, generate an image of the receivedgamma rays with the gamma ray image detector, and based on the generatedimage, determine an integrity of the at least one weld.

In an aspect combinable with the seventh example implementation, thenuclear waste includes spent nuclear fuel.

In an aspect combinable with any of the previous aspects of the seventhexample implementation, the spent nuclear fuel includes at least onespent nuclear fuel assembly.

In an aspect combinable with any of the previous aspects of the seventhexample implementation, the gamma ray source material includesAmericium-241.

In an aspect combinable with any of the previous aspects of the seventhexample implementation, the gamma ray source material is positioned at avertical location in the volume of the canister to vertically align withthe at least one weld.

In an aspect combinable with any of the previous aspects of the seventhexample implementation, the gamma ray source material is positioned ator near a radial centerline of the volume of the canister.

In an aspect combinable with any of the previous aspects of the seventhexample implementation, each of the housing, the top, and the weldmaterial includes the corrosion resistant alloy.

In an aspect combinable with any of the previous aspects of the seventhexample implementation, the corrosion resistant alloy includes CRA 625.

In an aspect combinable with any of the previous aspects of the seventhexample implementation, the at least one weld includes a horizontalweld.

In an aspect combinable with any of the previous aspects of the seventhexample implementation, a plurality of gamma rays emit from the gammaray source material and scatter through the volume of the nuclear wastecontainer and through one or more voids in the one or more welds towardthe gamma ray image detector.

In an aspect combinable with any of the previous aspects of the seventhexample implementation, at least one of the nuclear waste canister orthe gamma ray image detector is rotated during the receipt, at the gammaray image detector, of the gamma rays from the gamma ray source materialthat travel through the one or more voids in the weld.

In an aspect combinable with any of the previous aspects of the seventhexample implementation, at least one of the nuclear waste canister orthe gamma ray image detector is rotated for 360 degrees during thereceipt, at the gamma ray image detector, of the gamma rays from thegamma ray source material that travel through the one or more voids inthe weld.

In an aspect combinable with any of the previous aspects of the seventhexample implementation, the nuclear waste canister further includes agamma ray shield positioned in the volume and vertically between thenuclear waste and the gamma ray source material.

In an aspect combinable with any of the previous aspects of the seventhexample implementation, the gamma ray shield is positioned verticallybetween the at least one weld and the nuclear waste.

An eighth example implementation includes a method of sealing a nuclearwaste canister including inserting nuclear waste into an open volume ofa housing of a nuclear waste canister; preparing at least one of an edgeof an open end of the housing or an edge of a lid sized to fit on theopen end of the housing; attaching the edge of the open end of thehousing to the edge of the lid by spin welding the lid onto the housing;and enclosing the open volume of the housing to seal the nuclear wastewithin the nuclear waste canister.

An aspect combinable with the eighth example implementation furtherincludes attaching a flywheel to the lid; and rotating the flywheel tospin weld the lid onto the housing.

In an aspect combinable with any of the previous aspects of the eighthexample implementation, the flywheel is attached to a gamma ray shieldthat is part of or mounted on the lid.

An aspect combinable with any of the previous aspects of the eighthexample implementation further includes oscillating at least one of thehousing or the lid to spin weld the lid onto the housing.

In an aspect combinable with any of the previous aspects of the eighthexample implementation, at least one of the lid or the housing includesa corrosion-resistant metallic alloy.

In an aspect combinable with any of the previous aspects of the eighthexample implementation, the corrosion-resistant metallic alloy includesCRA 625.

In an aspect combinable with any of the previous aspects of the eighthexample implementation, preparing at least one of the edge of the openend of the housing or the edge of the lid includes preparing both of theedge of the open end of the housing and the edge of the lid.

In an aspect combinable with any of the previous aspects of the eighthexample implementation, preparing includes polishing or smoothing.

In an aspect combinable with any of the previous aspects of the eighthexample implementation, the spin welding includes welding the lid to thehousing without any filler or flux material.

In an aspect combinable with any of the previous aspects of the eighthexample implementation, the nuclear waste includes spent nuclear fuel.

A ninth example implementation includes a system for sealing a nuclearwaste canister that includes a nuclear waste canister and a spin weldingsystem. The nuclear waste canister includes a housing that defines anopen volume and a lid sized to fit on an open end of the housing. Theopen end of the housing includes an edge that mirrors an edge of thelid. The open volume of the housing is sized to enclose nuclear waste.The spin welding system is configured to attach the edge of the open endof the housing to the edge of the lid by spin welding the lid onto thehousing to enclose the open volume of the housing to seal the nuclearwaste within the nuclear waste canister.

An aspect combinable with the ninth example implementation furtherincludes a flywheel attachable to the lid, where the spin welding systemis configured to rotate the flywheel to spin weld the lid onto thehousing.

In an aspect combinable with any of the previous aspects of the ninthexample implementation, the flywheel is attached to a gamma ray shieldthat is part of or mounted on the lid.

In an aspect combinable with any of the previous aspects of the ninthexample implementation, the spin welding system is configured tooscillate at least one of the housing or the lid to spin weld the lidonto the housing.

In an aspect combinable with any of the previous aspects of the ninthexample implementation, at least one of the lid or the housing includesa corrosion-resistant metallic alloy.

In an aspect combinable with any of the previous aspects of the ninthexample implementation, the corrosion-resistant metallic alloy includesCRA 625.

In an aspect combinable with any of the previous aspects of the ninthexample implementation, at least one of the edge of the open end of thehousing or the edge of the lid is prepared prior to attachment.

In an aspect combinable with any of the previous aspects of the ninthexample implementation, the preparation includes polishing or smoothing.

In an aspect combinable with any of the previous aspects of the ninthexample implementation, the spin welding system is configured to weldthe lid to the housing without any filler or flux material.

In an aspect combinable with any of the previous aspects of the ninthexample implementation, the nuclear waste includes spent nuclear fuel.

A tenth example implementation includes a method of sealing a nuclearwaste canister that includes inserting nuclear waste into an open volumeof a housing of a nuclear waste canister; positioning a sub-lid on topof an edge of an open end of the housing; depositing a liquid orsemi-solid metal on top of at least one of the sub-lid or the edge ofthe open end of the housing; and sealing, with the liquid or semi-solidmetal, the open volume of the housing to seal the nuclear waste withinthe nuclear waste canister.

In an aspect combinable with the tenth example implementation, at leastone of the sub-lid, the liquid or semi-solid metal, or the housingincludes a corrosion resistant metallic alloy.

In an aspect combinable with any of the previous aspects of the tenthexample implementation, each of the sub-lid, the liquid or semi-solidmetal, and the housing includes the corrosion resistant metallic alloy.

In an aspect combinable with any of the previous aspects of the tenthexample implementation, the corrosion resistant metallic alloy includesAlloy 625.

In an aspect combinable with any of the previous aspects of the tenthexample implementation, the nuclear waste includes spent nuclear fuel.

In an aspect combinable with any of the previous aspects of the tenthexample implementation, each of the sub-lid and the edge of the open endof the housing is circular.

In an aspect combinable with any of the previous aspects of the tenthexample implementation, a circumference of the sub-lid is greater thanan inner circumference of the edge of the open end of the housing, andthe circumference of the sub-lid is less than an outer circumference ofthe edge of the open end of the housing.

In an aspect combinable with any of the previous aspects of the tenthexample implementation, depositing the liquid or semi-solid metal on topof at least one of the sub-lid or the edge of the open end of thehousing includes depositing the liquid or semi-solid metal to cover thesub-lid and a portion of the edge of the open end of the housing that isexposed by the sub-lid.

An aspect combinable with any of the previous aspects of the tenthexample implementation further includes depositing an amount of theliquid or semi-solid metal to form a lid of a particular thickness onthe housing of the canister.

In an aspect combinable with any of the previous aspects of the tenthexample implementation, depositing the liquid or semi-solid metal on topof at least one of the sub-lid or the edge of the open end of thehousing includes three-dimensionally (3D) printing the liquid orsemi-solid metal on top of at least one of the sub-lid or the edge ofthe open end of the housing.

An eleventh example implementation includes a system for sealing anuclear waste canister that includes a nuclear waste canister includinga housing that defines an open volume and a sub-lid sized to fit on anopen end of the housing, the open end of the housing including an edge,the open volume of the housing sized to enclose nuclear waste; and adirect metal deposition system configured to deposit a liquid orsemi-solid metal on top of at least one of the sub-lid or the edge ofthe open end of the housing and seal, with the liquid or semi-solidmetal, the open volume of the housing to seal the nuclear waste withinthe nuclear waste canister.

In an aspect combinable with the eleventh example implementation, atleast one of the sub-lid, the liquid or semi-solid metal, or the housingincludes a corrosion resistant metallic alloy.

In an aspect combinable with any of the previous aspects of the eleventhexample implementation, each of the sub-lid, the liquid or semi-solidmetal, and the housing includes the corrosion resistant metallic alloy.

In an aspect combinable with any of the previous aspects of the eleventhexample implementation, the corrosion resistant metallic alloy includesAlloy 625.

In an aspect combinable with any of the previous aspects of the eleventhexample implementation, the nuclear waste includes spent nuclear fuel.

In an aspect combinable with any of the previous aspects of the eleventhexample implementation, each of the sub-lid and the edge of the open endof the housing is circular.

In an aspect combinable with any of the previous aspects of the eleventhexample implementation, a circumference of the sub-lid is greater thanan inner circumference of the edge of the open end of the housing, andthe circumference of the sub-lid is less than an outer circumference ofthe edge of the open end of the housing.

In an aspect combinable with any of the previous aspects of the eleventhexample implementation, the direct metal deposition system is configuredto deposit the liquid or semi-solid metal to cover the sub-lid and aportion of the edge of the open end of the housing that is exposed bythe sub-lid.

In an aspect combinable with any of the previous aspects of the eleventhexample implementation, the direct metal deposition system is configuredto deposit an amount of the liquid or semi-solid metal to form a lid ofa particular thickness on the housing of the canister.

In an aspect combinable with any of the previous aspects of the eleventhexample implementation, the direct metal deposition system includes athree-dimensional (3D) printer.

A number of implementations have been described. Nevertheless, it willbe understood that various modifications may be made without departingfrom the spirit and scope of the disclosure. For example, exampleoperations, methods, or processes described herein may include moresteps or fewer steps than those described. Further, the steps in suchexample operations, methods, or processes may be performed in differentsuccessions than that described or illustrated in the figures.Accordingly, other implementations are within the scope of the followingclaims.

What is claimed is:
 1. A method for inspecting a weld of a nuclear wastecanister, comprising: positioning a gamma ray image detector near anuclear waste canister that encloses nuclear waste, the nuclear wastecanister comprising a housing that comprises a volume in which the wasteis enclosed and a top connected to the housing with at least one weld toseal the nuclear waste in the nuclear waste canister; receiving, at thegamma ray image detector, gamma rays from the nuclear waste that travelthrough one or more voids in the weld; generating an image of thereceived gamma rays with the gamma ray image detector; and based on thegenerated image, determining an integrity of the at least one weld. 2.The method of claim 1, wherein the nuclear waste comprises spent nuclearfuel.
 3. The method of claim 2, wherein the spent nuclear fuel comprisesat least one spent nuclear fuel assembly.
 4. The method of claim 1,wherein the gamma ray image detector comprises a pinhole camera or anAnger camera.
 5. The method of claim 1, wherein at least one of thehousing, the top, or a weld material comprises a corrosion resistantalloy.
 6. The method of claim 5, wherein each of the housing, the top,and the weld material comprises the corrosion resistant alloy.
 7. Themethod of claim 5, wherein the corrosion resistant alloy comprises CRA625.
 8. The method of claim 1, wherein the at least one weld comprises ahorizontal weld.
 9. The method of claim 1, wherein receiving the gammarays comprises receiving a plurality of gamma rays that emit from thenuclear waste and scatter through the volume of the nuclear wastecontainer and through one or more voids in the one or more welds towardthe gamma ray image detector.
 10. The method of claim 1, furthercomprising rotating at least one of the nuclear waste canister or thegamma ray image detector during the receiving, at the gamma ray imagedetector, of the gamma rays from the nuclear waste that travel throughthe one or more voids in the weld.
 11. The method of claim 10, whereinthe rotating comprises rotating at least one of the nuclear wastecanister or the gamma ray image detector for 360 degrees.
 12. The methodof claim 1, wherein the at least one weld that connects the top to thehousing comprises a seal formed with a direct material depositionsystem.
 13. A system for inspecting a weld of a nuclear waste canister,comprising: a nuclear waste canister that encloses nuclear waste, thenuclear waste canister comprising a housing that comprises a volumeconfigured to enclose the nuclear waste and a top connected to thehousing with at least one weld to seal the nuclear waste in the nuclearwaste canister; and a gamma ray image detector system positionedadjacent the nuclear waste canister and configured to perform operationscomprising: receiving gamma rays from the nuclear waste that travelthrough one or more voids in the weld; generating an image of thereceived gamma rays with at least one gamma ray image detector; andbased on the generated image, determining an integrity of the at leastone weld.
 14. The system of claim 13, wherein the nuclear wastecomprises spent nuclear fuel.
 15. The system of claim 14, wherein thespent nuclear fuel comprises at least one spent nuclear fuel assembly.16. The system of claim 13, wherein the gamma ray image detector systemcomprises a pinhole camera or an Anger camera.
 17. The system of claim13, wherein at least one of the housing, the top, or a weld materialcomprises a corrosion resistant alloy.
 18. The system of claim 17,wherein each of the housing, the top, and the weld material comprisesthe corrosion resistant alloy.
 19. The system of claim 17, wherein thecorrosion resistant alloy comprises CRA
 625. 20. The system of claim 13,wherein the at least one weld comprises a horizontal weld.
 21. Thesystem of claim 13, wherein the gamma ray image detector system isconfigured to receive a plurality of gamma rays that emit from thenuclear waste and scatter through the volume of the nuclear wastecontainer and through one or more voids in the one or more welds. 22.The system of claim 13, wherein at least one of the nuclear wastecanister or the gamma ray image detector system is configured to rotateduring operation of the gamma ray image detector system to receive thegamma rays from the nuclear waste that travel through the one or morevoids in the weld.
 23. The system of claim 22, wherein the at least oneof the nuclear waste canister or the gamma ray image detector system isconfigured to rotate 360 degrees during operation of the gamma ray imagedetector system to receive the gamma rays from the nuclear waste thattravel through the one or more voids in the weld.
 24. The system ofclaim 13, wherein the at least one weld that connects the top to thehousing comprises a seal formed with a direct material depositionsystem.